Symmetrical transistors as a.c. or d.c. switches and their applications in modulator and demodulator circuits
J. Evans, Deepender Gill, B.R. Moffitt · Journal of the British Institution of Radio Engineers · 1961
It is shown that a symmetrical circuit containing a symmetrical or near symmetrical transistor should exhibit lower voltage and current drift than the more conventional circuits. A circuit with asymmetry complementary to a near symmetrical transistor will perform almost as well as the symmetrical circuit and will have zero “contact potential”. Test results demonstrate that an equivalent input circuit drift rate in the range ± 1.5 μV/deg C from — 40°C to + 100°C can be expected for a very large percentage of any batch. The relationship between drift rate, circuit impedance and ambient temperature is examined. Various applications of these switches are discussed including modulators, demodulators and precision a.c. switches.