Simple PIN diode switch
- PIN diode attenuator and switch circuit using a single PIN diode
For applications where the ultimate performance is not required a single PIN
diode can be used. The circuit shown only requires a few components and is very
simple to implement. Nevertheless it is able to act as a switch for radio
frequency or RF applications and is adequate for many applications.
When a positive potential is applied to the control point current, this
forward biases the diode and as a result the radio frequency signal is able to
pass through the circuit. When a negative bias is applied to the circuit, the
diode become reverse biased and is effectively switched off. Under these
conditions the depletion layer in the diode becomes wide and does not allow
signal to pass.
Simple PIN diode attenuator and switch
Although in theory any diode could be used in this position, PIN diodes have
a number of advantages as switches. In the first place they are more linear than
ordinary PN junction diodes. This means that in their action as a radio
frequency switch they do not create as many spurious products. Secondly when
reverse biased and switched off, the depletion layer is wider than with an
ordinary diode and this provides for greater isolation when switching.
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