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Measuring Switching Times of NPN Transistors

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I watched an excellent video by W2AEW on transistor switching times and realised I had much to learn.  Here is a link to the video: W2AEW inspiration .  Practical experimenting is by far the most effective way for me to learn so I set up a testing circuit. Alan explains the theory and his circuit for testing switching times here:  Explanation This my circuit which includes a square wave source: This is the 74AC14 (hex inverter with Schmitt Trigger input) square wave generator.  Note a 100nF decoupling capacitor on pin 14 (Vcc) and all unused inputs tied to ground to reduce the noise on the square wave output. Output is 5V peak to peak at 3.482KHz.   The rise time is 2.7nS.  This very fast version of a hex inverter is required to provide those very fast edges otherwise the true transistor performance may not be detectable. Here is the test rig.  There are female headers with turned pins to insert transistors under test.  There are two 100 ohm resis...
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Stair step Voltage Ramp

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Here is a circuit that consists of two different pulse generators and an interesting pulse voltage integrator combined to produce a stair step voltage output.  It is my version copied from W2AEW Stair Step Generator .    My goal was to duplicate Alan's circuit and to experiment with adjustments to the timings and to see if any practical applications emerged. The output looks like this:   The purple stair-step trace is the target output; the blue trace is the train of pulses and the yellow trace is the reset pulse. Here is the complete circuit (the dashed blocks indicate the units that produce each of the traces above): KL0S provided an EXCELLENT explanation if how the circuit works:  KL0S explanation 555 Pulse Generator A common circuit using a 555 timer in astable mode to generate a train of square wave pulses.  Length of the positive pulse is controlled by RV1& R4 that charge C2 via a steering diode.   The variable resistor allows the p...
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