1. © Bob York Monostable or “One-Shot" +5 V 2N7000 330Ω 10 μF R 330Ω 33 kΩ 330Ω 2N3904 100 μF 100 kΩ +5 V Q1Q2 R C

2. © Bob York BiStable Q1Q2 R c1 R b2 R b1 R c2 V cc 330Ω 2N3904 10 kΩ +5 V SetReset

3. © Bob York Astable 330Ω 100 kΩ 330Ω 2N3904 10 μF +5 V

4. © Bob York Simple Schmitt Trigger R1R1 + - R2R2 Vin Vout Vref Vin Vout Vref

5. © Bob York LM393 This output stage requires a pull-up resistor for most applications

6. © Bob York Relaxation Oscillator + - R1R1 R2R2 RC +V s -V s V+V+ V-V- Pullup resistor (required for most LM393 comparator circuits) Single-Supply LM393 Implementation Voltage at this node sets triggering point. Additional 100k resistor to V+ is required because the low outptu state is 0V, not –Vs as in the dual supply implementation. Generic Dual-Supply Implementation

7. © Bob York Duty Cycle

8. © Bob York Simple PWM Circuit V+V+

9. © Bob York 555

10. © Bob York 555 Astable 4.7kΩ R1 22kΩ R2 100nF C Cf 12V Vs LM555CM Timer GND 1 DIS 7 OUT 3 RST 4 VCC 8 THR 6 CON 5 TRI 2 Output

11. © Bob York 555 PWM Speed Controller

12. © Bob York Fan Driver +12 V V in 2N7000 DC motor/fan M 0.1 μF 2N7000 R8R8 1 kΩ