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Although modern integrated circuit operational amplifiers ease linear circuit design, IC processing limits amplifier output power. Many applications, however, require substantially greater output voltage swing or current (or both) than IC amplifiers can deliver. In these situations an output “booster,” or post amplifier, is required to achieve the needed voltage or current gain. Normally, this stage is placed within the feedback loop of the operational amplifier so that the low drift and stable gain characteristics of the amplifier are retained.... [read more]

This circuit idea is certainly not new, but when it comes to making a trade-of between using a small, short-circuit proof transformer or a capacitive voltage divider (directly from 230 V mains voltage) as the power supply for a fan, it can come in very handy. If forced cooling is an afterthought and the available options are limited then perhaps there is no other choice. At low currents a capacitive divider requires less space than a small, short-circuit proof transformer.... [read more]

This circuit features automatic Exit/Entry delays, timed Bell Cut-off and System Reset. It has provision for normally-open and normally-closed switches and will accommodate the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia Sensors).... [read more]

Here is the circuit diagram of regulated power supply. It is a small power supply that provides a regulated voltage, adjustable between 1.5 and 35 volts at 1 ampere. This circuit is ready to use, you just need to add a suitable transformer. This circuit is thermal overload protected because the current limiter and thermal overload protection are included in the IC.... [read more]

It is a little collection of amplifiers in bridge connection. The output power is low and they are for general use. They can be used with small active loudspeakers, car stereos etc. The only restriction, is that we should use loudspeakers with resistance above 4 ohm.... [read more]

The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... After turn-on by P1 pushbutton, the LED illuminates for around 25 minutes, but then it starts to blink for two minutes, stops blinking for two minutes and blinks for another two just before switching the lamp off, thus signaling that the on-time is ending. If the user want to prolong the reading, he/she can earn another half-hour of light by pushing on P1. Turning-off the lamp at user's ease is obtained by pushing on P2.... [read more]