067-0681-01
The Tektronix 067-0681-01 is a pulse generator for adjusting the transient response of high frequency oscilloscopes such as the 475, 485, 7A11, 7A24, 7A19/7904, and 7A29/7104. It takes in a 60 to 100Vpp rectangular waveform (e.g., from the calibrator output of an oscilloscope) and produces a 250mVpp rectangular waveform with risetime less than or equal to 125 picoseconds. The input and output connectors are BNC. The gender of the pulse output connector is appropriate for connecting directly to a BNC input of an oscilloscope (i.e., with no cable between the pulse generator and the oscilloscope to spoil the risetime). A regular BNC cable is typically used for connecting the input that drives the 067-0681-01. The risetime of the input to to the 067-0681-01 is not important.
The circuit starts with a DC restorer. The output of the DC restorer turns a current source on and off. The current produced by the current source (at the collector of PNP Q1) is set by controlling the emitter current using 6.3V zener diode CR3, R1, R2, and Vbe of Q3. R1 is a 200-ohm potentiometer (assume 100 ohms). R2 is 390 ohms.
- (6.2V - 0.7V) / (100 ohms + 390 ohms) = 11.2mA
The output pulse is produced by a 10mA 2pF tunnel diode, part number 152-0177-02.