Analog Circuits Cookbook

Power supplies and devices 205

As the delayed turn-off circuit of Figure 7.4 also includes p-n-p and

n-p-n transistors, it should be a fairly simple matter to turn these into a

stabiliser along the lines of Figure 7.7, though with inverted polarity of

course. Such an analog timed stabiliser could be useful where the instrument

it powers might be troubled by the switching edges of the oscillator of

Figure 7.7. The battery voltage monitor of Figure 7.5 obviously cannot

usefully be connected across the output of a stabiliser, nor (although its

housekeeping current is only a fraction of a milliamp) would one want to

leave it permanently connecte ...