| 摘要 |
<p>Logic circuits based on a differential amplifier with the common emitters thereof being connected through a constant current source generally require the use of a reference voltage (Vr) and associated transistor for each such differential amplifier to provide the reference level against which the two inputs (A, B) are compared to obtain the necessary logic operations.
<??>In order to eliminate the requirement for the reference voltage and the transistor, the input signals (A, B-) are selected to have the same relative amplitude difference (VL) between the high and low levels thereof and one of the two input signals is further controlled to be shifted relative to the other one by an amount equal to 1/2 such selected amplifier difference. The differential amplifier (42, 44) has a constant current source (50) and the respective output circuits (56, 66) are connected in emitter-follower configuration having constant current source resistors (60, 70) across which the output voltages are taken. By selecting the relative resistor values, the desired shift (1/2 VL) of the relative output level can be obtained. By employing additional sets of transistors in the differential amplifier, multiple inputs are accommodated and by utilizing output circuits having selected resistor value relationships, corresponding multiple outputs are obtained. </p> |
