微处理机及计算机很容易地连接成象可控硅整流器、三端双向可控硅开关元件及VMOS场效应晶体管(FET)那样的电源转换装置。但是,在所有这些开关转换装置中,只有VMOSFET是唯一的可用作一种数字可编程序的可变电阻器模式.即通过在该晶体管栅极上改变电压VGS来实现,改变电压的方法是用一种接近线性方式依次调节该晶体管的漏—源沟道电阻。数—模(D/A)转换器为计算机产生一可变电压提供了合适的方法。图1示出了一种廉价,简易的4位D/A转换器,该转换器将一种 Microprocessors and computers are easily connected to power conversion devices such as thyristors, triacs and VMOS field effect transistors (FETs). However, of all these switching devices, only the VMOSFET is the only one that can be used as a digitally programmable variable resistor mode, ie by changing the voltage VGS across the gate of the transistor, the method of changing the voltage is The drain-source channel resistance of the transistor is adjusted in a nearly linear fashion. Digital-to-analog (D / A) converters provide a suitable method for generating a variable voltage for a computer. Figure 1 shows an inexpensive, simple 4-bit D / A converter that will be one