A test circuit employs use of first and second switches to operably charge a capacitor to over 500 volts and, thereafter, discharge energy stored in the capacitor to test an over-voltage protection circuit associated with a pin of a semiconductor device. When switched by a controller, the first switch couples a high voltage source to charge a capacitor. After completing this charge phase, the controller opens the first switch, decoupling the high voltage source from the capacitor. The controller then activates the second switch to couple the capacitor to the pin of the semiconductor device. During this discharge phase, energy in the capacitor discharges through the protection circuit of the semiconductor device. Use of a high-voltage dry reed vacuum relay as the first switch provides better isolation of the high voltage source from the capacitor, avoiding a presence of an unwanted residual voltage component in a simulated ESD test pulse.