Variable-Threshold Receiver Circuit
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
This variable-threshold receiver circuit permits the use of a 10% power supply tolerance and provides an increase in noise margin. T1 and T2 form a current switch. In a conventional current switch T2 would have a fixed base voltage. The base voltage of T2 represents the threshold of the receiver circuit. In the disclosed circuit the base of T2 is connected to the collector of T1 which results in feedback. This feedback causes the circuit threshold to vary with the input level. The Down level noise margin is defined as the voltage difference between the maximum Down level and the threshold. Similarly, the Up level noise margin is defined as the voltage difference between the minimum Up level and the threshold voltage. Thus, it can be seen that the variable threshold of the disclosed circuit provides increased noise margin.