![power amplifier circuit power amplifier circuit](https://circuitszone.com/wp-content/uploads/2020/06/power-amplifier-circuit-based-2n3055.png)
If it is higher than 50mV, check the circuit for any error. Before connecting the speaker, check the zero signal output voltage of the amplifier and in any case it should not be higher than 50mV.Power supply voltage must not exceed +55/-55 V DC.Use a +45/-45 V DC, 3A dual supply for powering the circuit.Assemble the circuit on a good quality PCB.Now adjust R8 so that the multimeter reads 16.5mV which corresponds to 50mA quiescent current. Next step is setting up the quiescent current and keep the preset R8 in minimum resistance and connect a multimeter across points marked X & Y in the circuit diagram. Set R1 at midpoint before powering up and then adjust it slowly in order to get a minimum voltage (less than 50mV0 at the output. The network comprising of capacitor C3 and resistor R19 improves high frequency stability and prevents the chance of oscillation. Preset R8 can be used for adjusting the quiescent current of the amplifier. Power amplification stage based on Q7 and Q8 which operates in the class AB mode. This is done in order to improve linearity and gain. The second differential stage is formed by transistors Q3 and Q6 while transistors Q4 and Q5 forms a current mirror which makes the second differential pair to drain an identical current. Resistors R3 and R2 sets the gain of the amplifier. Preset R1 is used for adjusting the voltage at the output of the amplifier. Transistor Q1 and Q2 form the input differential pair and the constant current source circuit built around Q9 and Q10 sources 1mA. Resistor R20 limits the input current to Q1 C7 bypasses any high-frequency noise from the input. IF unblocked, this DC voltage will alter the bias setting s of the succeeding stages. Circuit diagramĬapacitor C8 is the input DC decoupling capacitor which blocks DC voltage if any from the input source. The amplifier has a low distortion of 0.1%, a damping factor greater than 200, input sensitivity of 1.2V and the bandwidth is from 4Hz to 4 KHz. The amplifier can be also used as a subwoofer amplifier but a subwoofer filter stage has to be added before the input stage. This Hi-Fi amplifier circuit is suitable for a lot of applications like general purpose amplifier, guitar amplifier, keyboard amplifier. The amplifier operates from a +45/-45 V DC dual supply and can deliver 100-watts RMS into an 8-ohm speaker and 160-watt rms into a 4-ohm speaker. The transformer used must provide for alternative 1A 70 W / 8 ohm (mono) and 2.2 A for version 90 W / 4 ohms.A 100W MOSFET power amplifier circuit based on IRFP240 and IRFP9240 MOSFETs is shown here. At 4 ohms, these values are ± 34, respectively, ± 40 V. Rectified voltage for 70 W / 8 ohms version is ± 40 V to be in load, no load, this corresponds to about ± 47 V. R24 and R28 values are then 3k9, R26 and R28 are 220 ohms, and D5, D6 and R30 are all eliminated. 2 must also be changed when using a 4 ohm load.
![power amplifier circuit power amplifier circuit](https://i.stack.imgur.com/b0ORUm.png)
Current through control stage is quite small (about 7 mA) as T6 and T9 are Darlington power transistors. The input signal for T4/T8 transistor is taken from the T1's collector in combination with current source T5 forms a control stage class A for power transistors. Current through deferential stage is kept constant at 1 mA current source through the action of T3. The input signal is brought to the transistor T1 and the reaction is taken on the basis of T2. If the component values in parentheses are used can be connected speakers with 4 ohm impedance, in which case the amplifier maximum output power will be around 90 watts. This 70-90 watt power amplifier circuit based on transistors is capable of provide an output of 70W on a load of 8 ohms or 90W on a 4 ohms load. This 70-90 watt power amplifier circuit is designed using some power transistors and some other common electronic components, and is capable to provide a maximum output power of 90W.