Amateur radio circuits for LM 324. Operational amplifier LM324

Microcircuit series LM324 is a low-cost operational amplifier with direct differential input, intra-frequency unity gain compensation, and short-circuit protection.

One microcircuit housing contains four operational amplifiers independent of each other. They have a number of undeniable advantages over standard operational amplifiers used in single-supply circuits. The LM324 op-amp works well in a wide range of supply voltages: from 3 V to 32 V. The microcircuit is manufactured in SOIC and DIP packages.

LM324 Operational Amplifier Technical Data

• Supply voltage:
• - unipolar: 3...32 V.
• - bipolar: 1.5...16 V.
• DC voltage gain: 100 dB.
• Own current consumption: 700 µA.
• Input bias current (temperature compensated): 45 nA.
• Input offset voltage: 2 mV.
• The input common mode voltage range contains ground.
• The differential input voltage range reaches the supply voltage.
• Output voltage: from 0 to Upit. – 1.5 V.

Op-amp structure

LM324 Pin Assignment

Dimensions of the operational amplifier

Analogues of LM324

Below is a list of foreign and domestic analogs of the LM324:

• ULN4336N
• GL324
• LA6324
• IR3702
• HA17324
• MB3614
• NJM2902D
• SG324N
• TDB0124
• UA324
• TA75902P
• 1401UD2 (domestic equivalent)
• 1435UD2 (domestic equivalent)

LM324 connection diagram

AC Inverting Amplifier

In this version of the amplifier, the gain will be equal to: k = - R3/R1

Non-inverting AC amplifier

The gain of this type of amplifier is calculated using the following formula: k = 1 + R4/R1

Non-inverting DC amplifier

The gain is: k = 1 + R3/R2

Peak detector on LM324

Peak detectors are used to record the maximum signal value over a certain period of time.

Comparator on LM324 with hysteresis

The difference in input voltage values ​​at which the output switches (hysteresis) from one state to another is calculated using the following formula: H = (R1/(R1+R2))(Voh-Vol)

Some simple examples of using the LM324 op-amp

LED indicator of acoustic signal on LM324

The low-frequency signal from the amplifier output is fed to the inverting inputs of all LM324 operational amplifiers. Their direct inputs are connected to a circuit of constant resistors R2…R9. Using a variable resistor, you can set the required sensitivity of the LED indicator. Resistances R12…R19 limit the maximum current flowing through the LEDs.

are low-cost operational amplifiers with direct differential input, intra-frequency unity gain compensation, and short-circuit protection.

One microcircuit housing contains four operational amplifiers independent of each other. They have a number of undeniable advantages over standard operational amplifiers used in single-supply circuits. The LM324 op-amp works well in a wide range of supply voltages: from 3 V to 32 V. The microcircuit is manufactured in SOIC and DIP packages.

LM324 Operational Amplifier Technical Data

• Supply voltage:
• - unipolar: 3…32 V.
• - bipolar: 1.5…16 V.
• DC voltage gain: 100 dB.
• Own current consumption: 700 µA.
• Input bias current (temperature compensated): 45 nA.
• Input offset voltage: 2 mV.
• The input common mode voltage range contains ground.
• The differential input voltage range reaches the supply voltage.
• Output voltage: from 0 to Upit. – 1.5 V.

Op-amp structure

Pin assignment

Analogues of LM324

List of foreign and domestic analogs of LM324:

• ULN4336N
• GL324
• LA6324
• IR3702
• HA17324
• MB3614
• NJM2902D
• SG324N
• TDB0124
• UA324
• TA75902P
• 1401UD2 (domestic equivalent)
• 1435UD2 (domestic equivalent)

LM324 connection diagram

AC Inverting Amplifier

In this version of the amplifier, the gain will be equal to: k = - R3/R1

Non-inverting AC amplifier

The gain of this type of amplifier is calculated using the following formula: k = 1 + R4/R1

Non-inverting DC amplifier

The gain is: k = 1 + R3/R2

Peak detector on LM324

Peak detectors are used to record the maximum signal value over a certain period of time

Comparator on LM324 with hysteresis

The difference in input voltage values ​​at which the comparator output switches (hysteresis) from one state to another is calculated using the following formula: H = (R1/(R1+R2))(Voh-Vol)

Examples of using the LM324 operational amplifier

LED indicator of acoustic signal on LM324

The low-frequency signal from the amplifier output is fed to the inverting inputs of all LM324 operational amplifiers. Their direct inputs are connected to a voltage divider constructed from a chain of fixed resistors R2…R9. Using a variable resistor, you can set the required sensitivity of the LED indicator. Resistances R12…R19 limit the maximum current flowing through the LEDs.

Simple LED flasher based on LM324 op-amp

The circuit allows you to smoothly turn on and off the LEDs. The LED flasher is built on an LM324 operational amplifier and two transistors of different conductivities. The switching speed of the LEDs depends on the resistance of resistor R3 and the capacitance of capacitor C1.

The LM324 microcircuit consists of four identical operational amplifiers (op-amps) assembled in a single package, operating from a single power source over a wide voltage range. Each opamp includes an input differential stage, short-circuit protection and internal frequency correction at unity gain.

The characteristics and low cost of this device ensure its widespread use in amateur radio circuits and industrial electronics. It is ideal for use in compact, portable electronic devices.

It is produced in DIP-type packages: plastic CDIP, ceramic PDIP or SO-type for surface mounting: SOIC, TSSOP. Structurally, the device has 14 pins. Therefore, in some technical descriptions, the designation DIP-14 or SO-14 is found.

The assignment of pins for different cases is identical: 2,3, 5,6, 9,10, 13,12 - inputs, 1,7,8,14 - output, 4 - plus power supply, 11 - minus power supply.

Specifications

• Supply voltage range U supply. (V cc): unipolar source: +3…30 V, bipolar source: ±1.5…±15 V (V);
• Differential input voltage Udif.(V IDR): 32 V (V);
• Input ref. Uin. (V ICR) from -0.3…32 V (V);
• Input current I ICR (with negative V ICR) 5 mA (mA);
• Input current I ICR (with positive V ICR) 0.4 mA (mA);

Electrical parameters(at U supply +5 V and T A +25 °C):

• Input bias voltage Ucm (V IO) from 2...7 mV (mV);
• Input bias current Iin. (I IB) from 45...100 nA (nA);
• Output nap. Uout. (Vout): from 0… Upit. – 1.5 V (V);
• Gain (K): 100 dB;
• Bandwidth (f) 1 MHz;
• Current consumption without load I pot. (I CC): no more than 700 µA (µA);
• Input current difference (shift current) Isdv. (I IO) from 5...30 nA (nA);
• Power dissipation P P max (P tod) depends on the type of housing: PDIP 1130 mV (mW); CDIP 1260 mV(mW); SOIC 800 mW.
• Ambient operating temperature range T A: 0…+70°C;
• Storage temperature T storage (T str): -65… +150 °C.

The parameters of lm324 from different companies differ slightly from each other, so when developing your circuits, it is recommended that you familiarize yourself with the official technical documentation for the device used from a specific manufacturer.

Peculiarities.

The differential input voltage range reaches the supply voltage. For lm324, the lower limit of the input common-mode range is 0.3 V lower than V - , and the output voltage swing is limited below by V - . Both inputs and outputs have a limit value of 1.5V less than V+.

The unity gain frequency fi (from 100 KHz to 30 MHz), this is the frequency at which the gain of the microcircuit (K) becomes equal to unity (0 dB).

Has internal frequency equalization for unity gain.

The input common mode voltage range includes ground.

The short circuit duration T short circuit (Tsc) at the output is unlimited.

Description of work

The operation of the lm324n microcircuit is based on the simultaneous functioning of four op-amps inside it. All amplifiers are powered from the same power source, have inverting and non-inverting inputs and the same output. The power source can be unipolar or bipolar.

Let's look at the internal circuit of one of the single-supply operational amplifiers. Let's take it directly from the datasheet for LM324.

Functionally, each operational amplifier consists of: a differential stage, as well as intermediate and output amplification stages.

The differential cascade performs the functions of amplifying the difference between the voltages supplied to the input (V + and V -) and neutralizing common-mode signals. Provides high input resistance.

The intermediate stage provides balancing of the opamp (setting the output to zero voltage when the inputs are closed), matching the resistances of the differential and output stages, as well as frequency correction (protection against self-excitation).

The output stage provides low output impedance, load power requirement, current limiting and short circuit protection.

Marking

The LM series is based on integrated circuits manufactured by National Semiconductor. The prefix LM originally meant linear monolithic (linear, monolithic) and was used to designate general purpose amplifiers (General Purpose) for which there were no strict requirements. The numbers “324” indicate the serial number of the chip. The "-N" at the end of the serial number denotes devices purchased by Texas Instruments from National Semiconductor. In September 2011, National Semiconductor was taken over by Texas Instruments, which did not change the LM prefix on its products. Therefore, currently the LM marking is the Texas Instruments manufacturer code, but it is widely used by other manufacturers when releasing their analogues of this chip.

LM324 microcircuits and the same one with the letter N have the same physical and electrical characteristics. For many manufacturers, the symbols “-N” at the end of the marking indicate the plastic type of the microcircuit housing - DIP14.

It should also be noted that manufacturing companies are constantly improving their products. Currently, modifications that are superior in a number of functions have appeared, for example: LM324K, LM324KA with internal protection against electrical discharge (HBM ESD); micropower LP324 with current consumption of 21 μA; low-voltage LMV324, with supply voltage from 2.7 V to 5.5 V; LPV324, manufactured using BiCMOS technology and a current consumption of 9 µA, etc. Amplifiers with the symbol “A” in the marking, for example “LM324A-N”, will have better V IO characteristics compared to others (without “A”).

Analogue LM324

List of imported analogs of LM324: ULN4336N, GL324, LA6324, IR3702, HA17324, MB3614, NJM2902D, SG324N, TDB0124, UA324, TA75902P, Russian 1401UD2 and 435UD2.

Scope of application

The LM324 found its greatest popularity using standard negative feedback circuits. It is used in the creation of various multifunctional devices: integrators, differentiators, demodulators, logarithmic amplifiers, adders, adding-subtracting devices, amplitude regulators, generators, etc. Due to the constant improvement of the device in question, many different devices using lm324 appear, for example:

• motion sensor circuit for lighting;
• Neptune incubator thermostat diagram, etc.

Simple amplifier circuit using LM324

Let's consider one of the simplest circuits on LM324 with negative feedback (NFB) - a voltage follower. As a rule, studying a topic on op-amps begins with a voltage follower. This circuit is also called an amplifier whose voltage gain is equal to unity. Ideally, this means that the op-amp does not provide any signal amplification and the output voltage is the same as the input. That is, if 5 V is supplied to the input of the op-amp, then 5 V will be at its output.

But this statement is true for an ideal operational amplifier, and not for the LM324 discussed in the article. Since this is not a virtual, but a real microcircuit, its characteristics differ from ideal ones. Let's look at the graph of output voltage versus input voltage for lm324.

On the graph, area “A” shows the phase change at the output. This can happen when a negative voltage appears at the input of the microcircuit and can lead to undesirable consequences - its failure.

Also, the graph shows that the voltage at the output of the amplifier increases with increasing input. But it cannot grow indefinitely, and is limited by the 5 V supply voltage of the microcircuit and the features of its operation. Thus, the voltages at the inputs vary slightly, a small current flows through them, so the output voltage will differ slightly from the supplied one. On the graph, in area “C”, you can see the maximum output voltage of 3.8 V for the amplification circuit in question, powered from 5 V.

In practice, everywhere you have to work with active electronic components that have a fairly weak output current. For example, such as a microphone. Connecting an element with low resistance to it will reduce the voltage of the output signal created with its help. In such cases, you can use a voltage follower, which has a high input and low output impedance, and therefore will not reduce or distort the signal supplied to the input.

A voltage follower is far from the most common typical application for this microcircuit. Based on this op-amp, other standard solutions are created and continue to be improved, on the basis of which modern electronic devices operate.

LED flasher circuit on lm324

This circuit is quite simple and allows you to control the LEDs on and off quite smoothly. The flasher uses an additional two transistors. It is worth noting that the switching speed will depend on the capacitance of capacitor C1 and the base resistance of resistor R3.

Operational safety

Sometimes, not all lm324 channels are used in a project. If this is the case, then the unused ones should be connected in such a way as not to affect the others. See the manufacturer’s datasheet for options for connecting unused channels.

Under certain conditions, the polarity of the output voltage may become inverted, which may damage the chip. This is typical in comparator and voltage follower circuits. In order to avoid the appearance of negative voltage (phase inversion) at the input, manufacturers recommend adding a resistor in series to the non-inverting input of the circuit, which will limit the input current to 1 mA or lower. This amount of input current will reduce the risk of damage to the device.

All op amp inputs should not be directly connected to ground. It is always necessary to add some resistance to limit the current to 10 mA or less. All input pins must include a diode from input to Gnd. In circuits with two power supplies, the Gnd pin will be negative. However, during power-on, power-off, or when there is a sudden voltage fault, the Gnd pin may become positive. If this happens, a large current will flow through the grounded input pin, which can damage the chip.

Adding a series resistor from 1 kOhm to 10 kOhm at the input can prevent it from breaking. Do not connect to a power source with reverse polarity, as the lm324n may overheat and fail.

Manufacturers

Below are the datasheets of the main lm324 manufacturers.