High Voltage, High Power Transistors. Characteristics of Developmental Units.

The Radio Corporation of America, under the auspices of Office of Naval Research contract number NOBsr-81322, has continued development work on silicon power transistors. Eight state-of-the-art samples of this transistor, designated TA-1891, have been tested by the U.S. Naval Research Laboratory for voltage breakdown, output characteristics and saturation voltage. The breakdown voltage of these units is in the range between 400 and 500 volts, and the characteristic is stable, with no negative resistance region up to 500 volts. Output characteristics, although satisfactory, should be improved, particularly at low collector voltages. Gain and saturation voltage for these ten ampere units are excellent. A fifty percent improvement in the gain would result in a 20 to 25 ampere unit. Thermal resistance could probably be improved, but is, on the average, adequate at this time for 300 watts dissipation. Two transistors are capable of 450 watts dissipation at 25 C case temperature, even in the interim case provided.