LM324 is a general-purpose integrated quad operational amplifier. The main advantages are low cost and high cost performance. This article is mainly based on the circuit diagram analysis of the subwoofer of lm324n, only personal opinions, if there are deficiencies, I hope to advise.
LM324LM324 includes two independent operational amplifiers with high gain and internal frequency compensation . It is suitable for single power supply with a wide range of power supply voltage, and also suitable for dual power supply mode. Under recommended working conditions, the power supply current and power supply The voltage is irrelevant. Its application range includes sensor amplifiers, DC gain modules, and all other occasions that can be powered by a single power supply and use operational amplifiers. The package form of LM324 is plastic package 14-lead dual-in-line.
LM324 is a four-op-amp integrated circuit, it adopts 14-pin dual-in-line plastic package, the appearance is shown in the figure. It contains four groups of operational amplifiers with exactly the same form. In addition to power sharing, the four groups of operational amplifiers are independent of each other. Each group of operational amplifiers can be represented by the symbols shown in Figure 1. It has 5 pins, among which "+" and "-" are two signal input terminals, and "V+" and "V-" are positive and negative power supplies. Terminal, "Vo" is the output terminal. Among the two signal input terminals, Vi-(-) is the inverting input terminal, which means that the signal at the output terminal Vo of the op amp is opposite to the input terminal; Vi+ (+) is the non-inverting input terminal, which represents the signal at the output terminal Vo of the op amp. Same phase as this input terminal.
LM324 internal structure diagram
Features of LM324:
1. Dash protection output
2. True differential input stage
3. Can work with single power supply: 3V-32V
4. Low bias current: maximum 100nA (LM324A)
5. Each package contains 4 operational amplifiers.
6. With internal compensation function.
7. The common mode range is extended to the negative power supply
8. Industry standard pinout
9. The input terminal has electrostatic protection function
LM324 electrical parameters
Pin arrangement diagram
Circuit diagram analysis of subwoofer based on lm324n
Many audio equipment's spectrum analyzers use this circuit as a bandpass filter to select the signals of different frequency bands, and use the light-emitting diodes to indicate the magnitude of the signal amplitude on the display. The center frequency of this active bandpass filter, the voltage gain Ao=B3/2B1 at the center frequency fo, the quality factor, the 3dB bandwidth B=1/(п*R3*C) can also be determined according to the design Q, The fo and Ao values ​​are used to find the parameter values ​​of the various components of the band-pass filter. R1=Q/(2пfoAoC), R2=Q/((2Q2-Ao)*2пfoC), R3=2Q/(2пfoC). In the above formula, when fo=1KHz, C takes 0.01Uf. This circuit can also be used for general frequency selective amplification.
This circuit can also use a single power supply, just bias the positive input of the op amp at 1/2V+ and connect the lower end of the resistor R2 to the positive input of the op amp.
LM324 pinout diagram
When it is used as an audio amplifier, it is characterized by high input impedance. Among them, R1 and R2 form a 1/2V+ voltage divider circuit, and the op amp is biased through R3. The voltage amplification factor Av of the circuit is also only determined by the external resistance: Av=1+Rf/R4, and the circuit input resistance is R3. The resistance of R4 ranges from several thousand ohms to several tens of kiloohms.
Schematic diagram of subwoofer circuit based on lm324n
to sum upWhen LM is used in an audio amplifier, it acts as an operational amplifier and can have good sound quality, which is very suitable for equalization and heavy bass fields.
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