K155la3 description. Microcircuit K155LA3, imported analogue - microcircuit SN7400. What is contained in this case
First, let's look at the characteristics of the radio component.
1. The most important thing is nutrition. It is supplied to the 7 (-) and 14 (+) legs and amounts to 4.5 - 5 V. More than 5.5 V should not be supplied to the microcircuit (it begins to overheat and burns out).
2. Next, you need to determine the purpose of the part. It consists of 4 elements of 2i-not (two inputs). That is, if you supply 1 to one input and 0 to the other, then the output will be 1.
3. Consider the pinout of the microcircuit:
To simplify the diagram, it shows the separate elements of the part:
4. Consider the location of the legs relative to the key:
You need to solder the microcircuit very carefully, without heating it (you can burn it).
Here are the circuits using the k155la3 microcircuit:
1. Voltage stabilizer (can be used as a phone charger from a car cigarette lighter).Here's the diagram:
Up to 23V can be supplied to the input. Instead of the P213 transistor, you can install the KT814, but then you will have to install a radiator, since it can overheat under heavy load.
Printed circuit board:
Another option for a voltage stabilizer (powerful):
2. Car battery charge indicator.
Here's the diagram:
3. Tester of any transistors.
Here's the diagram: 
Instead of diodes D9, you can put d18, d10.
Buttons SA1 and SA2 are switches for testing forward and reverse transistors.
4. Two options for rodent repeller.
Here's the first diagram: 
C1 - 2200 μF, C2 - 4.7 μF, C3 - 47 - 100 μF, R1-R2 - 430 Ohm, R3 - 1 ohm, V1 - KT315, V2 - KT361. You can also supply MP series transistors. Dynamic head - 8...10 ohms. Power supply 5V.
Second option: 
C1 – 2200 µF, C2 – 4.7 µF, C3 – 47 - 200 µF, R1-R2 – 430 Ohm, R3 – 1 kohm, R4 - 4.7 kohm, R5 – 220 Ohm, V1 – KT361 (MP 26, MP 42, KT 203, etc.), V2 – GT404 (KT815, KT817), V3 – GT402 (KT814, KT816, P213). Dynamic head 8...10 ohm.
Power supply 5V.
The K155LA3 microcircuit, like its imported analogue SN7400 (or simply -7400, without SN), contains four logical elements (gates) 2I - NOT. The K155LA3 and 7400 microcircuits are analogues with complete pinout matches and very similar operating parameters. Power is supplied through terminals 7 (minus) and 14 (plus), with a stabilized voltage from 4.75 to 5.25 volts.
Microcircuits K155LA3 and 7400 are created on the basis of TTL, therefore - a voltage of 7 volts is for them absolutely maximum. If this value is exceeded, the device burns out very quickly.
The layout of the outputs and inputs of logic elements (pinout) of the K155LA3 looks like this.
In the picture below - electronic circuit a separate element 2I-NOT of the K155LA3 microcircuit.
Parameters of K155LA3.
1 Rated supply voltage 5 V
2 Low level output voltage no more than 0.4 V
3 High level output voltage not less than 2.4 V
4 Low level input current no more than -1.6 mA
5 High level input current no more than 0.04 mA
6 Input breakdown current no more than 1 mA
7 Current short circuit-18...-55 mA
8 Current consumption at low output voltage level no more than 22 mA
9 Current consumption at high output voltage level no more than 8 mA
10 Static power consumption per one logic element no more than 19.7 mW
11 Propagation delay time when turned on no more than 15 ns
12 Propagation delay time when turned off no more than 22 ns
Scheme of a rectangular pulse gerator on K155LA3.
It is very easy to assemble a rectangular pulse generator on the K155LA3. To do this, you can use any two of its elements. The diagram might look like this.
Pulses are removed between pins 6 and 7 (minus power) of the microcircuit.
For this generator, the frequency (f) in hertz can be calculated using the formula f = 1/2(R1 *C1). Values are entered in Ohms and Farads.
Use of any materials from this page is permitted provided there is a link to the site
Getting to know the digital chip
In the second part of the article, we talked about the conventional graphic symbols of logical elements and the functions performed by these elements.
To explain the principle of operation, contact circuits were given that perform the logical functions AND, OR, NOT and NAND. Now you can begin a practical acquaintance with the K155 series microcircuits.
Appearance and design
The basic element of the 155th series is the K155LA3 microcircuit. It is a plastic case with 14 pins, on the top side of which there is a marking and a key indicating the first pin of the microcircuit.
The key is a small round mark. If you look at the microcircuit from above (from the housing side), then the pins should be counted counterclockwise, and if from below, then clockwise.
A drawing of the microcircuit housing is shown in Figure 1. This housing is called DIP-14, which in English means a plastic housing with a double-row arrangement of pins. Many microcircuits have a larger number of pins and therefore the packages can be DIP-16, DIP-20, DIP-24 and even DIP-40.
Figure 1. DIP-14 housing.
What is contained in this case
The DIP-14 package of the K155LA3 microcircuit contains 4 2I-NOT elements independent of each other. The only thing they have in common is the common power pins: pin 14 of the microcircuit is the + power supply, and pin 7 is the negative pole of the source.
In order not to clutter the diagrams with unnecessary elements, power lines, as a rule, are not shown. This is also not done because each of the four 2I-NOT elements can be located in different places in the circuit. Usually on the diagrams they simply write: “Add +5V to pins 14 DD1, DD2, DD3...DDN. -5V connect to pins 07 DD1, DD2, DD3…DDN.” separately located elements are designated as DD1.1, DD1.2, DD1.3, DD1.4. Figure 2 shows that the K155LA3 microcircuit consists of four 2I-NOT elements. As already mentioned in the second part of the article, the input pins are located on the left, and the outputs on the right.
The foreign analogue of the K155LA3 is the SN7400 chip and it can be safely used for all the experiments described below. To be more precise, the entire K155 series of microcircuits is an analogue of the foreign SN74 series, so sellers on radio markets offer exactly this.
Figure 2. Pinout of the K155LA3 microcircuit.
To conduct experiments with the microcircuit, you will need a voltage of 5V. The easiest way to make such a source is to use the K142EN5A stabilizer chip or its imported version, called 7805. In this case, it is not at all necessary to wind a transformer, solder a bridge, or install capacitors. After all, there will always be some Chinese network adapter with a voltage of 12V, to which it is enough to connect 7805, as shown in Figure 3.
Figure 3. Simple power supply for experiments.
To conduct experiments with the microcircuit, you will need to make a small breadboard. It is a piece of getinax, fiberglass or other similar insulating material measuring 100*70 mm. Even simple plywood or thick cardboard is suitable for such purposes.
Along the long sides of the board, tinned conductors should be strengthened, about 1.5 mm thick, through which power will be supplied to the microcircuits (power buses). Holes with a diameter of no more than 1 mm should be drilled between the conductors over the entire area of the breadboard.
When conducting experiments, it will be possible to insert pieces of tinned wire into them, to which capacitors, resistors and other radio components will be soldered. You should make low legs at the corners of the board, this will make it possible to place the wires from below. The design of the development board is shown in Figure 4.
Figure 4. Development board.
Once the breadboard is ready, you can start experimenting. To do this, you should install at least one K155LA3 microcircuit on it: solder pins 14 and 7 to the power buses, and bend the remaining pins so that they are adjacent to the board.
Before starting experiments, you should check the reliability of the soldering, the correct connection of the supply voltage (connecting the supply voltage in reverse polarity can damage the microcircuit), and also check whether there is a short circuit between adjacent terminals. After this check, you can turn on the power and begin experiments.
For measurements, it is best suited with an input impedance of at least 10 Kom/V. Any tester, even a cheap Chinese one, fully satisfies this requirement.
Why is a pointer better? Because, observing the oscillations of the needle, you can notice voltage pulses, of course of a fairly low frequency. Digital multimeter does not have such ability. All measurements must be carried out relative to the “minus” of the power source.
After the power is turned on, measure the voltage at all pins of the microcircuit: at input pins 1 and 2, 4 and 5, 9 and 10, 12 and 13, the voltage should be 1.4V. And at output pins 3, 6, 8, 11 there is about 0.3V. If all voltages are within the specified limits, then the microcircuit is operational.
Figure 5. Simple experiments with a logic element.
You can start checking the operation of the 2I-NOT logical element, for example, from the first element. Its input pins are 1 and 2, and its output is 3. In order to apply a logical zero signal to the input, it is enough to simply connect this input to the negative (common) wire of the power source. If you need to apply a logical one to the input, then this input should be connected to the +5V bus, but not directly, but through a limiting resistor with a resistance of 1...1.5KOhm.
Let's assume that we connected input 2 to a common wire, thereby applying a logical zero to it, and a logical one to input 1, as just indicated through the limiting resistor R1. This connection is shown in Figure 5a. If, with such a connection, you measure the voltage at the output of the element, the voltmeter will show 3.5...4.5V, which corresponds to a logical one. A logical one will be obtained by measuring the voltage at pin 1.
This completely coincides with what was shown in the second part of the article using the example of a 2I-NOT relay circuit. Based on the results of the measurements, we can draw the following conclusion: when one of the inputs of the 2I-NOT element is high and the other is low, a high level is necessarily present at the output.
Next, we will perform the following experiment - we will apply one to both inputs at once, as indicated in Figure 5b, but we will connect one of the inputs, for example 2, to the common wire using a jumper wire. (For such purposes, it is best to use a regular sewing needle soldered to a flexible wire). If you now measure the voltage at the output of the element, then, as in the previous case, there will be a logical unit.
Without interrupting the measurement, remove the jumper wire and the voltmeter will show a high level at the output of the element. This fully corresponds to the logic of the operation of the 2I-NOT element, which can be verified by referring to the contact diagram in the second part of the article, as well as by looking at the truth table shown there.
If now this jumper is periodically connected to the common wire of any of the inputs, simulating the supply of low and high levels, then using a voltmeter you can detect voltage pulses at the output - the arrow will oscillate in time with the jumper touching the input of the microcircuit.
From the experiments carried out, the following conclusions can be drawn: a low-level voltage at the output will appear only when there is a high level at both inputs, that is, condition 2I is satisfied for the inputs. If at least one of the inputs has a logical zero and the output has a logical one, we can repeat that the logic of the microcircuit is fully consistent with the logic of the 2I-NOT contact circuit discussed in.
Here it is appropriate to do another experiment. The point is to turn off all the input pins, just leave them in the “air” and measure output voltage element. What is going to be there? That's right, there will be a logical zero voltage. This suggests that unconnected inputs of logical elements are equivalent to inputs with a logical one applied to them. You should not forget about this feature, although it is usually recommended to connect unused inputs somewhere.
Figure 5c shows how a 2I-NOT logic element can simply be turned into an inverter. To do this, just connect both of its inputs together. (Even if there are four or eight inputs, such a connection is quite acceptable).
To make sure that the output signal has a value opposite to the input signal, it is enough to connect the inputs to a common wire using a wire jumper, that is, apply a logical zero to the input. In this case, a voltmeter connected to the output of the element will show a logical one. If the jumper is opened, a low level voltage will appear at the output, which is exactly the opposite of the input.
This experience suggests that the operation of the inverter is completely equivalent to the operation of the NOT contact circuit discussed in the second part of the article. These are, in general, the wonderful properties of the 2I-NOT microcircuit. To answer the question of how all this happens, we should consider the electrical circuit of the 2I-NOT element.
Internal structure of the 2I-NOT element
Until now, we have considered a logical element at the level of its graphic designation, taking it, as they say in mathematics, for a “black box”: without going into details of the internal structure of the element, we examined its reaction to input signals. Now it's time to study the internal structure of our logic element, which is shown in Figure 6.
Figure 6. Electrical diagram logical element 2AND-NOT.
The circuit contains four transistors n-p-n structures, three diodes and five resistors. Between transistors there is direct communication(without coupling capacitors), which allows them to work with constant voltages. The output load of the microcircuit is conventionally shown as a resistor Rн. In fact, this is most often an input or several inputs of the same digital microcircuits.
The first transistor is multi-emitter. It is he who performs the 2I input logical operation, and the transistors following him perform amplification and inversion of the signal. Microcircuits made according to a similar circuit are called transistor-transistor logic, abbreviated TTL.
This acronym reflects the fact that input logic operations and subsequent amplification and inversion are performed by transistor circuit elements. In addition to TTL, there is also diode-transistor logic (DTL), the input logic stages of which are made on diodes located, of course, inside the microcircuit.
Figure 7.
At the inputs of the 2I-NOT logic element, diodes VD1 and VD2 are installed between the emitters of the input transistor and the common wire. Their purpose is to protect the input from voltage of negative polarity, which can arise as a result of self-induction of installation elements when the circuit operates at high frequencies, or is simply supplied by mistake from external sources.
The input transistor VT1 is connected according to a common base circuit, and its load is transistor VT2, which has two loads. In the emitter this is resistor R3, and in the collector R2. Thus, a phase inverter is obtained for the output stage on transistors VT3 and VT4, which makes them work in antiphase: when VT3 is closed, VT4 is open and vice versa.
Let's assume that both inputs of the 2I-NOT element are applied low. To do this, simply connect these inputs to a common wire. In this case, transistor VT1 will be open, which will entail the closing of transistors VT2 and VT4. Transistor VT3 will be in the open state and through it and diode VD3 current flows into the load - at the output of the element there is a high-level state (logical unit).
In the event that a logical one is applied to both inputs, transistor VT1 will close, which will lead to the opening of transistors VT2 and VT4. Due to their opening, transistor VT3 will close and the current through the load will stop. The output of the element is set to a zero state or a low level voltage.
The low level voltage is due to the voltage drop at the collector-emitter junction of the open transistor VT4 and, according to technical specifications, does not exceed 0.4V.
The high-level voltage at the output of the element is less than the supply voltage by the amount of the voltage drop across the open transistor VT3 and the diode VD3 in the case when the transistor VT4 is closed. The high level voltage at the output of the element depends on the load, but should not be less than 2.4V.
If a very slowly varying voltage varying from 0...5V is applied to the inputs of an element connected together, then it can be seen that the transition of the element from high to low level occurs abruptly. This transition occurs when the voltage at the inputs reaches approximately 1.2V. This voltage for the 155th series of microcircuits is called threshold.
Boris Alaldyshkin
Continuation of the article:
EBook -
Chip K155LA3 is, in fact, basic element 155th series of integrated circuits. Externally, it is made in a 14-pin DIP package, on the outside of which there are markings and a key that allows you to determine the beginning of pin numbering (when viewed from above - from a point and counterclockwise).
The functional structure of the K155LA3 microcircuit has 4 independent logical elements. There is only one thing that unites them, and these are the power lines (common pin - 7, pin 14 - positive power pole). As a rule, the power contacts of microcircuits are not depicted on circuit diagrams.
Each individual 2I-NOT element K155LA3 microcircuits in the diagram they are designated DD1.1, DD1.2, DD1.3, DD1.4. On the right side of the elements there are outputs, on the left side there are inputs. An analogue of the domestic K155LA3 microcircuit is the foreign SN7400 microcircuit, and the entire K155 series is similar to the foreign SN74.
Truth table of the K155LA3 microcircuit
Experiments with the K155LA3 microcircuit
Install the K155LA3 microcircuit on the breadboard and connect the power to the pins (pin 7 minus, pin 14 plus 5 volts). To take measurements, it is better to use a dial voltmeter with a resistance of more than 10 kOhm per volt. Why use pointer, you ask? Because, by the movement of the arrow, the presence of low-frequency pulses can be determined.
After applying voltage, measure the voltage on all legs of the K155LA3. If the microcircuit is working properly, the voltage at the output pins (3, 6, 8 and 11) should be about 0.3 volts, and at the pins (1, 2, 4, 5, 9, 10, 12, and 13) around 1.4 IN.
To study the functioning of the 2I-NOT logic element of the K155LA3 microcircuit, let’s take the first element. As mentioned above, its input is pins 1 and 2, and its output is 3. The logical 1 signal will be the plus of the power supply through a 1.5 kOhm current-limiting resistor, and the logical 0 will be taken from the minus of the power supply.
First experiment (Fig. 1): Let's apply logical 0 to pin 2 (connect it to the power supply minus), and pin 1 to a logical one (plus power supply through a 1.5 kOhm resistor). Let's measure the voltage at output 3, it should be about 3.5 V (logic 1 voltage)
Conclusion one: If one of the inputs is log.0, and the other is log.1, then the output of K155LA3 will definitely be log.1
Experiment two (Fig. 2): Now we will apply logic 1 to both inputs 1 and 2 and in addition to one of the inputs (let it be 2) we will connect a jumper, the second end of which will be connected to the power supply minus. Let's apply power to the circuit and measure the voltage at the output.
It should be equal to log.1. Now remove the jumper, and the voltmeter needle will indicate a voltage of no more than 0.4 volts, which corresponds to the log level. 0. By installing and removing the jumper, you can observe how the voltmeter needle “jumps”, indicating changes in the signal at the output of the K155LA3 microcircuit.
Conclusion two: Signal log. There will be 0 at the output of the 2I-NOT element only if both its inputs have a logic level of 1
It should be noted that unconnected inputs of the 2I-NOT element (“hanging in the air”) leads to the appearance of a low logical level at the K155LA3 input.
Experiment three (Fig. 3): If you connect both inputs 1 and 2, then from the 2I-NOT element you get a logical NOT element (inverter). By applying log.0 to the input, the output will be log.1 and vice versa.
From 10.08.2019 to 07.09.2019 technical break.
We will resume accepting parcels from 09/08/2019.
Acceptance of microcircuits (MS) 155, 172, 555, 565 series, prices
This page presents 155 series microcircuits and similar ones in black and brown plastic cases. Our company accepts microcircuits of other series according to high prices from private individuals on an ongoing basis for more than 6 years. You can reliably and safely for you.
It is worth noting that the price for the 155 series and others like it is calculated by the weight of the microcircuits when the parts arrive at our office for evaluation by specialists. We are often asked the same question: I have about 50 grams of KM capacitors, 200-400 grams of 155 series microcircuits and a few other parts. Can I send them in a parcel?
We answer everyone: Yes, you can. Send as many as you have. The calculation will always be made in full. The highest prices are for series 565,555,155 microcircuits with a yellow (gold-plated) substrate-plate inside. If you want to get the maximum benefit from the sale, then you need to bite through each microcircuit and look for the presence of a yellow backing plate, since in the 155,555 series there are often empty microcircuits with a white backing inside, instead of the required gold-plated backing. This will be shown in the photographs below.
The price of microcircuits of these series directly depends on the year of manufacture, manufacturer and acceptance conditions (military, civilian, and so on).
Also, MC 155, 172, 176, 555, 565 series and other similar series must be cut off from the boards before being sent in a parcel by Russian Post and sent to our company only in this form, without the boards themselves. Since sending on boards leads to an increase in the cost of the parcel due to the greater weight and if only these chips on boards are sent in the parcel. If there are few boards with these microcircuits (MC), up to 5-7 units (boards), then send the MC on the boards as is, along with other radio parts and components.
You often come across boards that contain some microcircuits with yellow pins in a ceramic case and some 155 series and similar microcircuits in a black plastic case. Such boards can be sent as is, without removing parts from the boards.
In this case, the calculation will be made after our specialists remove the MS from the boards. Ceramics (white, pink), 133, 134 series and the like will be counted individually, MS in a black plastic case will be weighed and the MS data markings will be inspected. This will not change the price downwards.
For more information on microcircuits, see the following pages:
Photos and prices for microcircuits
| Appearance | Marking/Price | Appearance | Marking/Price |
|---|---|---|---|
| K155LA2 Price: |
KR140UD8B Price: |
||
| K155IE7 partial yellow leads Price: |
K155LI5 Price: |
||
| K157UD1 Price: |
K155LE6 Price: |
||
| K118UN1V Price: |
K1LB194 Price: |
||
| K174UR11 Price: |
KM155TM5 Price: |
||
| KR531KP7 Price: |
KS1804IR1 Price: |
||
| K555IP8 Price: |
KR537RU2 Price: |
||
| KR565RU7 Price: |
K561RU2 Price: |
||
| KR590KN2 Price: |
KR1021ХА4 Price: |
||
| KR1533IR23 Price: |
Microcircuits-mixture Price: |
||
| KR565RU1 without parts of yellow legs Price: |
KR565RU1 with partly yellow legs Price: |
||
| K155KP1 Price: |
K155ID3 Price: |
||
| K174ХА16 Price: |
KR580IK80 Price: |
||
| KR573RF5 Price: |
KR537RU8 Price: |
||
| K555IP3 Price: |
KR572PV2 Price: |
||
| K561IR6A Price: |
K145IK11P Price: |
||
| K589IR12 Price: |
KR581RU3 Price: |
All rights reserved 2012 - 2019
All materials on this site are subject to copyright (including design). Copying, distribution, including by copying to websites on the Internet, or any other use of information and objects without the prior consent of the copyright holder is prohibited.
We draw your attention to the fact that all information is for informational purposes only and under no circumstances constitutes a public offer as defined by the provisions of Article 437 of the Civil Code of the Russian Federation.
