The proposed simple electronic spy Bug circuit is basically a high gain amplifier using the IC 741 as the heart of the circuit and also a couple of high gain output transistors. The IC 741 if configured as a non-inverting amplifier which performs the function of a pre-amplifier stage. The gain of this IC 741 preamplifier stage may be varied as desired, using the pot across its input and output pin outs. The gain setting is used to set the sensitivity of the amplifier and is set to maximum so that even low volume speech conversation may be picked through it. The mic at the input transforms sound vibrations into minute electrical pulses, which is further amplified by the IC 741 to suitable levels before applying it to the output amplifier stage consisting of a standard DARLINGTON stage. This Darlington stage is made using a couple of high gain transistors bc107A’s.

The proposed simple electronic spy Bug circuit is basically a high gain amplifier using the IC 741 as the heart of the circuit and also a couple of high gain output transistors. The IC 741 if configured as a non-inverting amplifier which performs the function of a pre-amplifier stage. The gain of this IC 741 preamplifier stage may be varied as desired, using the pot across its input and output pin outs. The gain setting is used to set the sensitivity of the amplifier and is set to maximum so that even low volume speech conversation may be picked through it. The mic at the input transforms sound vibrations into minute electrical pulses, which is further amplified by the IC 741 to suitable levels before applying it to the output amplifier stage consisting of a standard DARLINGTON stage. This Darlington stage is made using a couple of high gain transistors bc107A’s.