THRESHOLD VALUE SWITCHING CIRCUIT

摘要

PURPOSE:To attain threshold switching setting with high accuracy by using two transistors (TRs) having an identical characteristic to switch the threshold value and controlling the setting of threshold value with high accuracy by a resistor and a reference power supply independently of the saturated voltage of the TRs. CONSTITUTION:An input voltage is applied to a non-inverting input of a comparator OP1, the comparator OP1 compares the input voltage VIN with an inverting input voltage Vth and outputs the result as a voltage Vout. Then a current of an input TRQ3 of a current mirror comprising the TRs Q3, Q4 connected to the output is controlled to allow the output TRQ4 to control a TRQ0 in the threshold switching TRs Q1, Q0 to actuate the TRQ1 for the threshold value change. It is possible to decrease the setting error from nearly 10% of a conventional threshold value switching using a low reference voltage into an error of 1% or below by providing the paired TRs for the threshold value switching. Thus, the comparison with high accuracy is attained even when the reference voltage is low without being affected by the saturated voltage of the TRs.