In the given threshold circuit, the threshold voltage Vth equals VsAT divided by (RH/R1).

In the given threshold circuit, the threshold voltage Vth equals VsAT divided by (RH/R1).

• A. VsAT/(RH/R1)
• B. VsAT*(RH/R1)
• C. VsAT
• D. R1/RH

Answer: (A)

Threshold voltage in this kind of circuit comes from the portion of the saturated output that is fed back to the input through the resistor network. When the amplifier sits at its saturated level, VsAT, the node that establishes the switching threshold sees a fraction of that VsAT determined by the resistor ratio, specifically R1 divided by RH. That gives Vth = VsAT × (R1/RH), which is exactly the same as VsAT divided by (RH/R1). So the threshold voltage scales with the feedback fraction: larger RH relative to R1 lowers the threshold, while a larger R1 relative to RH raises it. The other forms either miss the division by the resistor network or yield a non-voltage quantity, so they don’t match the actual threshold behavior.

Threshold voltage in this kind of circuit comes from the portion of the saturated output that is fed back to the input through the resistor network. When the amplifier sits at its saturated level, VsAT, the node that establishes the switching threshold sees a fraction of that VsAT determined by the resistor ratio, specifically R1 divided by RH. That gives Vth = VsAT × (R1/RH), which is exactly the same as VsAT divided by (RH/R1). So the threshold voltage scales with the feedback fraction: larger RH relative to R1 lowers the threshold, while a larger R1 relative to RH raises it. The other forms either miss the division by the resistor network or yield a non-voltage quantity, so they don’t match the actual threshold behavior.