107

The Tektronix 107 is a squarewave generator. The signal starts with an astable multivibrator composed of both halves of a 6BQ7A dual triode tube. The multivibrator circuit is cathode coupled to a pulse shaping circuit, and then to an output stage made from a single 6AU6 tube with a 50-ohm plate load, providing a controlled 50-ohm output impedance. The 50-ohm plate load keeps the voltage gain of output stage low, and the bandwidth high.