- Joined
- Jun 20, 2013
- Messages
- 696
- Location
- Kapiti Coast, New Zealand
- Tagline
- Path under Coastlands overbridge
Schematic:
This is a bridge amplifier circuit that I designed and built a long time ago to deliver 100 watts into a low ohm load, less than 1 ohm, several pairs of 4 or 2 ohm speakers in parallel. I originally designed it to run off a 13.8 volt power supply (10 - 15 volts) and up to 40 volts with modifications. I designed it for automotive and home use, but later I built several amplifier modules for use in a physics laboratory for a variety of experiments including infrasonic.
It has a frequency range of 0 Hz (DC) to well above 20kHz.
This circuit works very well although several design improvements are needed to improve DC stability,
keep quiescent output voltage at exactly 50% of power supply voltage, additional temperature compensation and protection against thermal runaway, overload, short circuit protection and thermal shutdown.
The protection circuit and thermal switch shown in the schematic is a proposed modification and not actually in use.
There is a diode in reverse bias across each of the four MJ802 / MJ4502 output transistors not shown in the schematic.
I originally used 2N3055, MJ2955 complimentary transistors in the output stage but later on purchased 30 amp MJ802, MJ4502 transistors on special.
An unusual phase splitting method is used in the driver stage.
Complimentary drivers 2N6387, 2N6667 are darlington transistors.
Voltage gain is adjusted by changing the value of the 75 ohm resistors in the output voltage divider networks connected to the negative feedback loops.
This is a bridge amplifier circuit that I designed and built a long time ago to deliver 100 watts into a low ohm load, less than 1 ohm, several pairs of 4 or 2 ohm speakers in parallel. I originally designed it to run off a 13.8 volt power supply (10 - 15 volts) and up to 40 volts with modifications. I designed it for automotive and home use, but later I built several amplifier modules for use in a physics laboratory for a variety of experiments including infrasonic.
It has a frequency range of 0 Hz (DC) to well above 20kHz.
This circuit works very well although several design improvements are needed to improve DC stability,
keep quiescent output voltage at exactly 50% of power supply voltage, additional temperature compensation and protection against thermal runaway, overload, short circuit protection and thermal shutdown.
The protection circuit and thermal switch shown in the schematic is a proposed modification and not actually in use.
There is a diode in reverse bias across each of the four MJ802 / MJ4502 output transistors not shown in the schematic.
I originally used 2N3055, MJ2955 complimentary transistors in the output stage but later on purchased 30 amp MJ802, MJ4502 transistors on special.
An unusual phase splitting method is used in the driver stage.
Complimentary drivers 2N6387, 2N6667 are darlington transistors.
Voltage gain is adjusted by changing the value of the 75 ohm resistors in the output voltage divider networks connected to the negative feedback loops.
Last edited: