SaM - Carrier Amplifier

• $\varphi$ or $\varphi (V_g)$ is defined as $\mathrm{sign}(V_g)$.
• If $\varphi$ is high, the switch $S_1$ is ON, and $S_2$ is OFF.
• If $\varphi$ is low, $S_1$ is OFF, and $S_2$ is ON.
• NOTE: The resistance between $+$ and ground can assume any value ($R$, not just $R_1$).

This amplifier changes the sign of the input signal $V_0$, based on the sign of the signal $V_g$, so we will obtain as output signal $V_0^{\prime }=V_0\cdot \mathrm{sign}(V_g)$

• So if $V_0$ is “in phase”, meaning it has the same sign as $V_g$ ⇒ $V_0^{\prime }$ will be positive, otherwise if it is “not in phase”, $V_0^{\prime }$ will be negative.

If we wish to just get the sign of $V_0^{\prime }$, so to know if $V_g$ and $V_0$ are “in phase”, we can use an LPF (Low Pass Filter):

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Memory Card

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