| 摘要 |
<p>Apparatus herein provides for a chosen level of power dissipation of a resistor (30), for example, the heating element of a thermal head assembly. The resistance of the resistor (30) changes upon a change in temperature thereof, for example, due to increased flow of a current therethrough. The apparatus includes a resistive shunt (40) in series with the resistor (30), a first differential amplifier (42), with voltage drop across the resistor (30) being provided to first and second input terminals (44, 46) of the first differential amplifier (42), and a second differential amplifier (48), voltage drop across the shunt (40) being provided to first and second input terminals (50, 52) of the second differential amplifier (48). The output signals from the first and second differential amplifiers (42, 48) are provided to a voltage multiplier (62). The output signal from the voltage multiplier (62) is provided to an input terminal (66) of a power operational amplifier (68), and a programming sequence voltage is supplied to another input terminal (72) of the power operational amplifier (68). The output signal from the power operational amplifier (68) is provided to the resistor (30).</p> |
