Receiver Circuit With External Threshold Voltage Adjustment
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
The circuit shown in Fig. 1 translates off-chip signal voltage levels to on-chip voltage levels, the output remaining in phase with respect to the input. By its use, receiver threshold variations (normally a function of process parameters and temperature) are compensated for through a positive power supply voltage adjustment in the following manner. Transistor T2, with its associated components, forms a DTL (diode-transistor logic) like output buffer, assuring voltage levels compatible with DTL signal levels. Transistor T1, a "free" (it can be partially integrated into the structure of T2 without additional process steps) PNP, performs the actual voltage level translation. Diode D1 and resistor R1 isolate the base of T1 from the off-chip (input) line. When the input is high, T1 has no VBE and therefore is turned off.