| 摘要 |
<p>The present invention discloses a circuit for providing a variable output signal in response to a physical parameter sensed by a sensor in the circuit, preferably a force sensing resistor. The current mirror may consist of two transistors having common bases. Flow of current through the first transistor flows through the sensor and through a parallel resistor. This current is mirrored in a second transistor which provides flow of current which may either be used as an output signal or, more preferably, as a base current for a transistor which is used to control output signal voltage. The circuit uses the current mirror in connection with the sensor to eliminate the need for a negative voltage supply. The circuit may further advantageously contain a voltage limiter module which is used to limit the voltage which may be applied across the sensor if the range of input signals or the desired range of output signals exceeds the sensor's capability. The voltage limiter module establishes a fixed voltage across the sensor which is lower than the expected input or the desired output voltage ranges. The resistor in parallel with the sensor is used to ensure that a current is applied to the transistor in the voltage limiter module so that the transistor may maintain its operation as an emitter follower. The circuit may also be used with thermistors for temperature compensation.</p> |
