Skema Rangkaian Power Amplifier 2000 Watt

It is imperative that Q5 (the bias servo transistor) is mounted on the heatsink, in excellent thermal contact. This is because, unlike most of my other designs, this amp uses conventional Darlington output configuration. It is necessary to use a Darlington arrangement (or a low power Darlington transistor as shown) for Q5 to ensure that the bias remains at a safe value with temperature. There is probably good cause to model and test this aspect of the design very carefully, because it is so important. The arrangement as shown will reduce quiescent current at elevated temperatures. For example, if total Iq at 24°C is 165mA, this will fall to ~40mA at 70°C. This is probably fine, because there is some delay between the a power 'surge' and the output transistors transferring their heat to the bias servo via the heatsink.

The circuit is completely conventional, using a long tailed pair input stage, direct coupled to the VAS. No current mirror was used for the LTP, as this increases open loop gain and may give rise to stability issues. In a very high power amp, stability is paramount. The amp must never oscillate under any normal load condition, because the heat created can cause almost instant transistor failure.

The power supply needed for an amp of this size is massive. Grown welding machines will look at it and cry. For intermittent operation, you need a minimum of a 1000VA transformer (or 1500VA for the 2000W version), and it will have to be custom made because of the voltages used. If you expect to run the amp at continuous high power, then transformers should be 2kVA and 3000VA respectively. Filter capacitors will pose a problem - because you need caps rated for 150V, these will be hard to find. Because high voltage high value caps can be difficult to find, it may be necessary to use two electros in series for each capacitor location. This is the arrangement shown. You must include the resistors in parallel - these equalise the voltage across each capacitor so that they have the same voltage. Remember to verify the ripple current rating! This can be expected to be over 10A, and under-rated capacitors will blow up.

Another difficulty is the bridge rectifier. Although 35A bridges would seem to be adequate, the peak repetitive current is so high that they may not be up to the task. I suggest that you use two (or even three) in parallel as shown. The bridge rectifier voltage rating should be a minimum of 400V, and they must be mounted on a substantial heatsink.