Sunday, May 29, 2016

A curve tracer using AC.

I posted a poor mans curve tracer which was polarlized using pulsating DC to create the trace. This one uses AC and is non-polarized.

R1 is 2.2k Ohm with a 12 VAC transformer. Here are some sample traces.
 A 2N383 Emitter to Collector. It is a negistor see the reverse break over?

  This one is a capacitor. Ideally it would be an oval but my digital scope doesn't seem to understand oval

  This one is an Emitter to Base curve.
 A 2N2222 Emitter to Collector.
 A GS109 Emitter to Collector.
 Another Emitter to Collector.
  Power diode no breakover at top.
Signal diode see the break over at the top of the curve.
A resistor.

Monday, May 23, 2016

Example of FETs in radio.

Circuit to use to analyze dual gate circuits.

Dummy antenna

Used to connect test equipment. Matches the test equipment impedance to the antenna load impedance so the alignment doesn't shift when the generator is removed and the antenna connected.

Saturday, May 21, 2016

Poor man's curve tracer

Tried to build a simple curve tracer today. It does work. Used a broken wall wart, three terminal and four diodes. After I built I tried a SPICE model to draw the diagram and run a simulation. Here is the drawing.
D5 is the device under test. The scope X-Y leads go across R2 and D5 with the ground in the center.Here are some screen shots of diodes being tested.

 The wall wart I used was rated 15 Volts. You could go a little higher or lower but 15V gave good results for diodes, LED and transistor junctions.