Power Supply Circuit

Posted on Feb 7, 2014

The circuit consists of N-MOSFET voltage follower T1 (common Drain) and current source T2 (NPN Darlington). Current source is set to 2. 2 Amps. With 40V of supply voltage the circuit is able to deliver about 17W into 8 Ohm loudspeaker. But takes 88W from power supply anytime. Bandwidth (-3dB) is from 4Hz to 250kHz. Rise time is 1. 5 us. Output resis

Power Supply Circuit
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tance 0. 16 Ohm. The circuit is very tolerant to different kinds of load. Input resistance is 10 kOhm (R0), but can be increased up to 100 kOhm (R4) when omitting R0. Input capacitance remains high, about 1500 pF. For this reason, the preamp should not have higher output impedance than 1 kOhm to maintain high frequency limit about 100 kHz. An input potentiometer can be used instead of R0. If the value of the potentiometer is 5 kOhm then the high frequency limit will be about 70 kHz. The power follower can be connected directly to the output of CD player and for reduction of volume the potentiometer 5 kOhm can be used. Rod Elliott`s DoZ preamp is used (see or ). An article describing the use of this MOSFET power follower with Rod`s preamp can be seen at as "Project 83". The schematic of the DoZ preamp ( ©Rod Elliot, ESP, see his pages, and you can also order PCB`s for the DoZ from him. ) modified for this purpose can be seen in Fig. 2. To fulfill the specs of Q1-Q3 transistors, a supply voltage +Vs should be 30V. An experiment shows that they will survive supply voltage of 40V, so it is up to you to make a decision. It might be better to use BC547/BC557 as they are rated at 45V. When interconnecting the DoZ and the Follower, it is necessary to omit the R0 resistor of the follower. This slightly modified circuit can be seen in Fig. 3. The complete amplifier is shown in Fig. 4. As shown, the gain is 3. 2, so it will require...

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