For example, if R 1 is 1kΩ with R 2 and R 3 equal to 10kΩ, the circuit has a gain of 10, and if R 1 is 100kΩ, the gain is 0.1 (an attenuation of 10). If the value of R 1 is higher than R 2 and R 3, the circuit can accept higher input voltages because it acts as an attenuator. If the value of R 1 is made lower than R 2 and R 3, the circuit has gain. This property can be used to make non-linear amplifier circuits which have either logarithmic or anti-logarithmic (exponential) input to output relationships.ħ.1 Half-wave rectifier with filter capacitor or peak detector Also as we discovered in chapter 5 the diode voltage, in the forward conduction region, is exponentially related to the current through the diode. This characteristic can be used to make a voltage (actually current) dependent attenuator. In these situations it is often desirable to effectively cancel or correct for the forward voltage drop of the diode to accurately measure the required value of the signal.Īnother property of the diode is that the small signal conductance (or resistance) of the diode is a function of the DC current flowing through the diode (the operating point). There are other cases where a time varying signal might need to be converted into a DC signal. In chapter 6 we discussed the use of the diode as a means to convert AC power into DC power. In this chapter we will investigate a variety of circuits that make use of certain characteristics of the PN junction diode.
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