284
The Tektronix 284 is a pulse generator. Its output modes include:
- 70ps risetime pulse, 200mV, 50kHz repetition rate, 1us pulse duration (5% duty cycle)
- 1GHz sine wave, 100mV
- 100MHz sine wave, 100mV
- 10MHz square wave, 10mV, 100mV, or 1V
- 1MHz square wave, 10mV, 100mV, or 1V
- 100kHz square wave, 10mV, 100mV, or 1V
Only one mode can be used at a time. The pulse comes out one output connector. The sine wave and square wave come out another output connector. Both outputs are 50-ohm GR-874.
The 284 generates a 1GHz sinewave using an 2N3478 RF NPN transistor-based oscillator.
The 284 generates the 70ns risetime pulse using a 21mA tunnel diode, D180, Tektronix part number 152-0329-00. D180 is mounted inside of a 50-ohm airline (rigid coaxial transmission line with only air between the center conductor and the shell). D180 is in series with the airline's center conductor. One end of the airline contains three resistors for biasing the tunnel diode and terminating the transmission line. The other end of the airline is the GR-874 pulse output connector. For each pulse (every 20us):
- the biasing current is switched on, putting D180 close to its peak current
- a capacitively coupled "tripper" applies a short current pulse to D180, causing it to switch to its high-voltage state
- the biasing current is switched off, causing the tunnel diode to fall back to the low-voltage state
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Tunnel diode in housing
