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Using a Diode as a Signal Switch
- Diodes have a low resistance if they are forward biased.
- Diodes have an extremely high resistance when they are reverse biased.
- By switching the bias from forward to reverse, the diode can be "turned on or off" like a switch.
- This circuit only works for AC signals.
- As there are quite large DC voltage changes when the circuit switches, there could be unpleasant clicks in the output.
- The DC voltage clicks can be eliminated by slowing down the rate at which the DC voltages swing. The RC timing circuits on the logic input achieve this quite well.
- Reversing the diode direction changes the switch from normally open to normally closed.
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