The problem asks us to find the AC signal output, $V_o$, of the given circuit. The circuit consists of a $3 \sin(\omega t)$ mV AC signal source and a 5 V DC source in series, a 1 k$\Omega$ resistor, and two diodes (Germanium and Silicon) connected in series.
2025/5/29
1. Problem Description
The problem asks us to find the AC signal output, , of the given circuit. The circuit consists of a mV AC signal source and a 5 V DC source in series, a 1 k resistor, and two diodes (Germanium and Silicon) connected in series.
2. Solution Steps
First, consider the DC portion of the circuit. The DC source is 5V. Germanium diodes have a forward voltage drop of around 0.3V and Silicon diodes have a forward voltage drop of around 0.7V.
Since the diodes are in series and pointing in opposite directions, we analyze the positive and negative cycles separately. For the positive part of the AC input, the silicon diode will conduct (assuming the 5V source is positive). For the negative part of the AC input, the germanium diode will conduct.
We need to consider the AC input signal of mV.
The AC signal is small compared to the diode turn-on voltage. Therefore, the circuit acts like a clipping circuit.
During the positive cycle of the AC signal, the Silicon diode will be forward biased when the input voltage is greater than about 0.7 V. However, since the 5V DC source is in series with the AC signal, the silicon diode conducts during the positive AC cycle. The silicon diode will have a voltage drop of .
During the negative cycle of the AC signal, the Germanium diode will be forward biased when the input voltage is greater than about 0.3 V. Again, because of the 5V DC source, the germanium diode conducts during the negative AC cycle. The germanium diode will have a voltage drop of .
Therefore, the circuit clips the voltage when the top diode(Germanium) or bottom diode(Silicon) conducts.
The output voltage will be the input AC signal when neither diode is conducting. When the voltage reaches the diode cut in voltage the output will be clipped at around 0.3 V(Germanium) during negative parts of the signal and 0.7 V(Silicon) during positive parts of the signal.
The germanium diode will conduct when the input voltage goes below -0.3 V, and the silicon diode will conduct when the input voltage goes above 0.7 V.
Given a mV input, we can represent the output as clipped versions of it. However, given that the input AC signal amplitude is only 3 mV, it is much smaller than both 0.3 V and 0.7 V diode turn on voltages. As a result, the AC signal never gets close enough to those voltages for the diodes to conduct and clip the output. Thus the AC signal appears without any clipping on .
3. Final Answer
mV