那些要求远程增益控制的应用场合可以用Dallas Semiconductor公司的DS1666数字音频电阻器来加以简化.一个主要优点是,它既可配用,也可不配用微处理器/控制器.该电路只需3个IC和一个5V电源,就可通过PC打印机端口提供增益控制(参见附图a部分).U_1被接成运算放大器U_2的反馈电阻,而当U_1的电阻为零时,则加上R_2来提供一个完整的回路.ICL7660电源变换器 IC(U_3)配置成只按反转方式工作,以便从+5V中提供-5V电源.附图的b部分示出了从打印机端口加到U_1的输入信号.有两个重要的时延:T_(CI)和T_(IL)T_(CI)是(?)变成低态和(?)变成低态之间的最小时间,而T_(IL)则是(?)应当保持低态来从U/(?)信号中选通数据的最小时间.如果U/(?)为高态,则滑动片在增量 Applications that require remote gain control can be simplified by using the Dallas Semiconductor DS1666 digital audio resistor One major advantage is that it can be used with or without a microprocessor / controller, which requires only 3 ICs and a 5V power supply to provide gain control through the PC printer port (see Figure a). U_1 is connected to the feedback resistor of op amp U_2, and to R_2 when U_1’s resistance is zero A complete loop. The ICL7660 power converter IC (U_3) is configured to operate only in reverse mode to provide -5V from +5 V. Section b of the figure shows the input signal added to U_1 from the printer port. There are two important delays: T_ (CI) and T_ (IL) T_ (CI) are the minimum times between ()) going low and ()) going low and T IL (IL) (?) Should be kept low to select the minimum time for the data from the U / (?) Signal. If U / (?) Is high, the slider will increment in increments