| 摘要 |
PURPOSE:To obtain high current driving ability, to realize two-way current driving, and to perform accurate control by constituting a voltage-current conversion type current driving amplifier of BTL(Balanced Transformerless) constitution by using two negative feedback amplifiers, and putting a load in the negative feedback path of one amplifier. CONSTITUTION:The BTL circuit consists of the two amplifiers 1 and 2 and a coil L which is, for example, an inductive load is driven with a current. An input signal Vin is supplied to the inverted input terminals of operational amplifiers 1 and 2 in common through a resistance R1. A reference voltage Vref is supplied to the uninverted input terminals in common. Therefore, an output current I0 is determined by I0=-R2+R3/RsR1. (Vin-Vref). In said equation, a varying component is only an input signal Vin, so the output current I0 varies corresponding to the voltage level of the input signal Vin. The output current I0 flows through the coil L, but the amplifiers 1 and 2 are small in output imped ance and the current flows in both ways as shown by an arrow according to the change in the polarity of the input signal Vin.
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