Question

A signal conditioning circuit suitable for a push-pull type capacitive transducer is given in figure. The output $V_0$ is

• A. $V_0=E\frac{C}{\Delta C}$
• B. $V_0=E\frac{\Delta C}{C}$
• C. $V_0=E\frac{C-\Delta C}{C+\Delta C}$
• D. $V_0=E\frac{C+\Delta C}{C-\Delta C}$

Answer 1

The correct option is B $V_0=E\frac{\Delta C}{C}$

$V_{cd}=2E$

$V_0=V_{ba}$

$V_{bd}=\frac{C+\Delta C}{C+\Delta C+C-\Delta C}\times 2E$

$V_{ba}=V_{bd}-E$

$=\frac{C+\Delta C}{2C}\times 2E-E$

$=(\frac{C+\Delta C}{C}-1)E=\frac{\Delta C}{C}E$