Extreme Circuits

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Simple White Noise Generator

This two-transistor white noise generator has a surprising feature – about 30dB more noise than the more traditional designs. Q1 and Q2 can be any small-signal transistors with a beta of up to 400. The reverse-biased emitter-base junction of Q1 provides the noise source, which is fed into the base of Q2. Q2 forms a simple amplifier with a gain of 45dB. The improved output level is due mainly to the inclusion of C1, which provides a low-impedance AC source to the noise source while not disturbing the DC bias of Q1.

Circuit diagram:

The low amount of feedback also makes this circuit very resistant to oscillations and tolerant to circuit layout. Unfortunately, the truism of “no such thing as free lunch” also applies; C1 makes the circuit very sensitive to power supply ripple.

Source: Silicon Chip January 2005

Tags: White Noise, transistor, Circuit, Generator

Comments on this post:

Jacques Pelletier

1 year ago:  Connecting C1 from the emitter to the GND instead of +12V should solve the problem.

Gerda Frank
By Gerda Frank (0) 0Score: 

9 months ago:  You can connect C1 to GND from Emitter terminal..... it will solve your problem... I have tested it and its working...

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