Wiring Schematic Diagram

The Schematic Diagram is a basic MOSFET amplifier. Output power is 100 Wrms under 8 ohms or 160 Wrms under 4 ohms with distortion is 0.001 %. Bandwidth at -3 db is from 4 Hz to 100 Khz .

Input sensitivity is 1.2 volts. The gain of 27DB is archived by R7/R6. It may be modified by changing R7 value. Transistors T5 and T6 makes the second differential stage. Transistors T3 and T4 works as a current mirror source. They push the second differential stage to drain equal current. Doing so we get a high gain and an excellent linearity. Output MOSFET transistors works in AB class, their quiescent current is set at 100 mA trough P1. For setting quiescient current, you must set P1 in minimal resistance, place a multimeter in mV DC range on R14 or R15 leads, turn slowly the screw until you read a 33 mV value, which correspond to a 100 mA quiescent current.

F1 and F2 works as an elementary output short-circuit protection. The power supply must have a value between 45 and 55 Volts DC (positive and negative). One heatsink with a thermal resistance less of 2° C / W is required.

All resistors are 1% metal film 1/4 watt. Before connecting a speaker to the amplifier output, connect a multimeter to the output and look on DC output voltage. This level must not be greater than 50 mV. If it is so, check all amplifier for error. Also, change T2 with another device and check again. This amplifier is very simple to build and low cost.

The DS1802 is a dual audio taper-potentiometer having logarithmic resistive characteristics over the device range. Each potentiometer provides 65 wiper positions with a 1 dB increment per step and device mute. The DS1802 has two methods of device control, which include contact closure (pushbutton) inputs and a 3-wire serial interface for wiper positioning. The pushbutton control inputs provide a simple interface for device control without the need for a CPU. While the 3-wire serial interface, using a CPU, provides the user the ability of reading or writing exact wiper positions of the two potentiometers. The DS1802 can also be configured to operate in either independent or “stereo” modes when using pushbutton control. Independent mode of operation allows for independent wiper control, and stereo mode of operation provides single input control over both potentiometer wiper positions. The DS1802 is offered in commercial temperature versions. Packages for the part include a 20-pin DIP, 20-pin SOIC, and 20-pin TSSOP.