| 摘要 |
A circuit (10) receives a cyclic input signal having a frequency determined by a source (11), which frequency may vary in accordance with a parameter or condition to be measured, for example. The circuit (10) very precisely provides an output current representative of the frequency of the input signal. In particular, the circuit uses a pair of regulated and different voltages (16) (17), one (16) of which is impressed upon an averaging circuit (30) for a preselected time during each cycle of the input signal, and the other voltage (17) is impressed upon the averaging circuit (30) during the time when the first signal is not connected to the averaging circuit. A control signal (Vo) is developed from the averaging circuit (30) which is a function of the average of the voltage provided to the averaging circuit, and the control signal (Vo) in turn is used for controlling a current control amplifier (60) and transistors (61) (62) which in turn control current flow through a load (40) connected to output terminals (36) (37) and through a feedback resistor (63). The use of regulated voltage sources (16) (17) for deriving the current control signal insures great stability, relatively low cost, and precise operation. |
