Voltage High-Pass Circuit

If the input voltage is far enough over the zener voltage, current will flow through to the output with minimal losses through the zener diode. Due to the way the transistors are used, there is a noticeable voltage drop of over 2V and a resistor is needed to counteract inaccuracies in the transistors (ideal Beta values are 0.01, 1, and 100; effective Beta values are ~0.0098, ~0.99, and 100).