Direct Display of Varying Current Ratio

The ratio of two currents in function of any third quantity may be measured directly with the aid of pulse techniques. Sample pulses are taken from both currents by the same gating process while the duty cycle is changed in order to keep the time average of the pulsed denominator current constant. The time average of the numerator current is then proportional to the ratio of both currents. This principle is extremely useful for the investigation of electron devices when a large-signal parameter is displayed as a function of the operating point or of another variable. This paper describes two applications, the measurement of anode current/screen-grid current ratio as a function of control-grid voltage and that of the large-signal amplification factor as a function of emitter current in transistors.