Introduction to the Use of Operational Amplifier Circuit Based on LM324

Ⅰ. Overview of LM324 operational amplifier

Ⅱ. Four different packages of LM324 operational amplifier

Ⅲ. Functions of LM324 operational amplifier

Ⅳ. Maximum ratings of LM324 operational amplifier

Ⅴ. Characteristics of LM324 operational amplifier

Ⅵ. Circuit description of LM324 operational amplifier

Ⅶ. Applications and application circuits of LM324 operational amplifier

Ⅷ. Detection of LM324 operational amplifier

LM324 is a four-way operational amplifier (op-amp) manufactured by Texas Instruments in the United States. It is a low-power, low-noise, high-gain general-purpose operational amplifier that is widely used in various circuits.

The LM324 is a quad op amp integrated circuit with true differential inputs. It contains four sets of identical operational amplifiers inside. It has an ambient temperature range of 0°C to 70°C and a maximum junction temperature of up to 150°C. In addition, it comes in a 14-pin dual-in-line plastic package. This quad amplifier offers some significant advantages over standard op amps for single-supply applications. It can operate from supplies as low as 3 volts to as high as 32 volts with a quiescent current that is only one-fifth that of the MC1741. In addition, its common-mode input range includes the negative supply, eliminating the need for external biasing components in many applications.

Replacements and equivalents:

• LA6324

• LM224D

• CA324G

• MC3403N

• MLM224P

• UPC324C

• XR3403CN

The LM324 is available in four different packages as well as different sizes as follows.

• TSSOP package: 5mm x 4.4mm

• PDIP package: 19.18mm X 6.35mm

• CDIP package: 19.56mm X 6.67mm

• SOIC package: 8.65mm X 3.91mm

1. Filtering

LM324 chip can also be used for filtering, especially in audio filtering. It can handle both high-frequency and low-frequency signals, and is important for technologies that require different filters in different parts of the circuit for audio processing. LM324 based filters can help to eliminate noise in the circuit and reduce the distortion of the audio signal.

2. Common mode suppression

The topology and design features of the LM324 chip give it excellent rejection of common mode signals, which makes it ideal for use in circuits that require rejection of common mode signals. Common mode signals usually refer to the interference that exists between two input signals. By using the LM324, we can effectively suppress this common mode interference.

3. Amplifying voltage signals

The LM324 chip can also be used to amplify voltage signals, for example in sensor input and filter circuits. After receiving the input voltage, by adjusting the gain of the amplifier, we can get a higher voltage output signal. In addition, the LM324 can be used as an adjustable gain amplifier based on the current differential amplifier architecture.

    Unless there are special requirements, TA=25°C.

• It has lower power consumption.

• The LM324 features a short-circuit protection output function that effectively safeguards the circuit against short-circuits and other abnormal conditions.

• ESD clamping at the input improves reliability without affecting device operation.

• The input impedance of the LM324 is approximately 2MΩ, which means it can accept higher impedance input signals while helping to reduce the loading effect on the input source.

• LM324 has built-in external power supply compensation pin. By connecting external capacitors and resistors, it can significantly improve performance and stability. Additionally, the LM324 has an external frequency compensation pin. By connecting external capacitors and resistors, it can adjust the bandwidth of the amplifier to suit different application needs.

The LM324 series is made with four internally compensated two-stage operational amplifiers. The first stage of each circuit in this series consists of a differential input device with an input buffer transistor and a differential single-ended converter. The first stage performs not only the first stage gain function but also the level shifting and transconductance reduction functions. By reducing the transconductance, we can use a smaller compensation capacitor (only 5.0 pF), thus saving chip area.

This design feature helps improve the stability of the circuit by separating the collectors of Q20 and Q18 to reduce transconductance. Another advantage of this input stage is that in single-supply operation its input common-mode range can be varied between the negative supply or ground without adverse effects on the input device or the differential single-ended converter. Next is the second stage, which consists of a standard current source load amplifier stage. This stage can provide a higher output voltage range and has excellent voltage and temperature stability.

1. What are the applications of LM324?

Applications for the LM324 include sensor amplifiers, DC gain blocks, and all traditional operational amplifiers. For example, direct operation of the LM324 series can provide the required interface circuits in digital systems without the need for additional ±15V power supplies with standard 5V supply voltages.

2. Three application circuits of LM324

(1) Function generator circuit

Below is a function generator circuit built using the LM324 op amp chip.

As shown in the picture, the LM324 is powered by DC voltage through pins 4 and 11. We feed any voltage from 5V to 15V into pin 4-VCC and any voltage from -5V to -15V into pin 11-GND. This provides the circuit with enough power to operate.

The first op amp produces a square wave. The 100KΩ potentiometer is an important tool that allows us to change the frequency of the circuit and is also the key to adjusting the frequency of the output signal. So after the first op amp, we've got a square wave. Next, we get to the integrator circuit. Input the square wave into the integrator and we will get the triangular wave output. After the second op amp, we have the triangle wave as the second waveform. We then feed this triangle wave into another integrator circuit, and at this point, we get a sine waveform. After the third op amp, we have the third waveform, which is the sine waveform.

The first op amp produces a square wave. We feed this square wave into the integrator circuit, which now outputs a triangle wave. Next, we feed this triangle wave into a second integrator circuit to produce a sine wave. The 100KΩ potentiometer provides a fairly wide frequency range, so the circuit has good frequency regulation performance, similar to a standard function generator. Additionally, this circuit allows for easy amplitude adjustment. If we use a DC source to power the circuit, we can change the amplitude of the signal simply by adjusting the voltage on the DC source. However, if we choose to use battery power, we will need to add a corresponding number of batteries to achieve the required maximum voltage. We then add a small value potentiometer(200Ω~ 500Ω) to allow for voltage adjustment.

(2) LM324 non-inverting AC amplifier circuit

Non-inverting AC amplifiers are characterized by high input impedance. R1 and R2 form a 1/2V+ voltage divider circuit to bias the op amp. Its voltage amplification coefficient Av is determined by the external resistor Rf/R4: Av=1+Rf/R4. The input resistance of the circuit is R3, and the resistance of R4 ranges from a few thousand ohms to tens of thousands of ohms.

(3) LM324 inverting AC amplifier circuit

The LM324 amplifier can replace the triode for AC amplification and is used as the preamplifier of the amplifier. The specific circuit diagram is shown below.

The LM324 inverting AC amplifier circuit does not require debugging. The amplifier operates from a single power supply. The bias circuit consists of R1 and R2 to form 1/2V+, and C1 is a vibration suppression capacitor to provide stable bias. The voltage amplification factor Av is determined only by the external resistors Ri and Rf: Av=-Rf/Ri. Among them, the negative sign means that the output signal is in phase with the input signal. Av=-10 given in the figure, then the input resistance is Ri. Typically, Ri is first equal to the internal resistance of the signal source, and then Rf is chosen based on the desired amplification. Co and Ci are coupling capacitances.

LM324 is composed of four identical operational amplifiers, so the forward and reverse resistance values of each functional pin to ground are basically the same. We take pins 8, 9, and 11 of LM324 as an example to introduce its detection method and resistance value (the detection method of other pins is the same). We use the diode scale of the multimeter to measure.

(1) We use a black test lead to connect to pin 11 and a red test lead to pin 8. The resistance is 1997 ohms. We use b black test lead to connect to pin 8 and the red test lead to pin 11. The resistance is approximately 658 ohms. We use c black test lead to connect to pin 9 and red test lead to pin 11. The resistance is infinite. We use d black test lead to connect to pin 11 and the red test lead to pin 9. The resistance is approximately 712 ohms. We use e black test lead to connect to pin 10 and the red test lead to pin 11. The resistance is infinite. We use f black test lead to connect to pin 11 and the red test lead to pin 10. The resistance is approximately 711 ohms.

(2) Detection of resistance value of power supply terminal to ground

The power supply terminals of LM324 are pins 4 and 11. We only need to measure the resistance of the positive and negative resistors. The specific operations are as follows:

① We use the black test lead to connect to pin 4 and the red test lead to pin 11. The resistance is approximately 581 ohms. This step indicates that pin 4 is the positive pole and pin 11 is the negative pole. At the same time, we can also confirm the normal connection of the internal circuit of LM324.

② We use the black test lead to connect to pin 11 and the red test lead to pin 4. The resistance is approximately 1.272 kilohms. The resistance change in this step is very small, indicating that there is no short circuit or abnormality in the internal circuit.

In conclusion, when using the LM324 chip, we should choose it according to the specific application and performance, and pay attention to its related parameters and pin connection. When designing the circuit, we should fully consider signal input, output, isolation, power supply and other issues to ensure the normal operation of the op amp.

Frequently Asked Questions

1. What is the purpose of LM324?

An LM324 circuit is an operational amplifier that you can use on various types of circuits. It features a broad range of power supply, uptake of small static power, and compatibility to a single power supply.

2. Is LM324 single supply?

The LM324 series are low−cost, quad operational amplifiers with true differential inputs. They have several distinct advantages over standard operational amplifier types in single supply applications.

3. Is LM324 good for audio?

Yes. You can make an audio filter using the LM324 and some passive components. Could that make a high quality filter: nope. Any designer that is serious about audio quality will not use an LM324, the NE5532 is often a better choice. It needs a higher supply voltage though.

4. What is the difference between LM324 and LM393?

So, in short, the LM324 has frequency compensation to allow a wide variety of feedback configurations whereas the LM393 doesn't have this compensation and, to make things worse from a stability point of view, it has a further stage of voltage gain.

5. What is the difference between LM324 and LM324N?

LM324N and LM324AN do not share the same silicon die. There will be subtle differences, but both are compliant to the data sheet parameters. LM324-N (this 'N' represents National Semiconductor, not package type) is a third silicon die and has a different data sheet.