class A amplifier re-considered

Power supplies are always useful, and, in spite of the fact that integrated voltage regulators are now becoming quite readily available, a circuit using only standard ccmponents may be of interest. To avoid wasting too much power, and to limit the dissipation in the series regulator, the total 0-30 V control range is subdivided into three smaller ranges. Each of the three ranges corresponds to an appropriate secondary supply voltage (selected by SI a) and an appropriate reference voltage (selected by SI b).