- Minimalist Oscilloscope
- Switchable Output Crystal Oscillator
- Simple White Noise Generator
- Triangle / Squarewave Generator
- 1KHz Sinewave Generator
- Reverse Bias Oscillator
- Function Generator
- Oscilloscope testing module (huntron circuit)
- Triangle and Squarewave Generator
- Low Frequency Sinewave Generators
Simple White Noise Generator
Description
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.