Importance

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Abstract

An electrical circuit for generating a polynomial function in response to a linear input signal is disclosed. The circuit in one embodiment comprises a primary and a secondary current mirror, with the collector or source of the secondary current mirror connected in common with the input signal of the primary current mirror. The output signal of the electrical circuit is taken at the mirrored current source terminal of the first current mirror. The primary and secondary current mirrors are biased to at least initially respond exponentially to the linear input signal. Each then transitions into the more linear, resistor-dominated range. The primary current mirror is enabled at a predetermined cut-in level, such that an upward curving exponential response function is generated in response thereto. The second current mirror being conducting at a later level of the input signal, but increases more quickly than the primary current mirror so as to gradually deplete the primary current mirror and cause the output signal to transition into a downward sloping exponential function at a predetermined transition point and at a predetermined peak signal amplitude. The output signal then gradually declines to a predetermined cut-out level, where it reaches zero. The circuit can be constructed using BJT or MOS devices and a single transistor can be used in place of the second current mirror. Tuning can be achieved with fusible link tuning resistors and with multiple emitter transistors, as well as with multiple output devices on the primary current mirror, which are digitally controlled for selecting the peak output signal level during operation.

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First Claim