Abstract: A simple circuit technique is described to increase the bandwidth of digital potentiometers by a factor of 10 to 100. Using this technique can enable digital potentiometers to be used in high frequency applications at video bandwidths.
Digital potentiometers (or digital pots, or digipots) are extremely useful for controlling or adjusting circuit parameters. Normally they are src="/data/attachment/portal/201007/ET33815201007230417391.gif">
Figure 1. Typical Digital Poteniometer circuit configuration.
NOTE: With the inclusion of an op amp, the circuit can be used for gain, as well as attenuation. However, regardless of the circuit topology chosen, the method for increasing bandwidth—illustrated below—applies.
To calculate the transfer function of the circuit (VOUT/VIN), it is useful to use a different model for the potentiometer - see Figure 2. In this figure, R2 has been broken into R2top and R2bottom, where R2top is the portion of the resistance above the wiper, and R2bottom is the portion of the resistance below the wiper. Assuming we are using a pot with a 10kΩ end-to-end resistance (and neglecting the affect of wiper resistance), the ideal transfer function of R2top and R2bottom vs. digital code is as shown in Figure 3. The two end-points and the mid-point of the transfer function are useful to note: (1) When the Pot code = 0, R2top = 10kΩ and R2bottom = 0kΩ
(2) When the Pot code = Mid-Scale, R2top = R2bottom = 5kΩ
(3) When the Pot code = Full-Scale, R2top = 0kΩ and R2bottom = 10kΩ
Figure 2. The digital Pot with R2 broken into R2top and R2bottom.
本人用IRS2110 HO 端始输出奇怪的波形本人买的是IRS2110 （和IR2110不一样吗），LO一直可以输出，HO 输出一个很乱的波。于是我把自举二极管拿了。发现VS脚还会输出一个矩形不规则波（并没有给VS脚通电）
怎么个
1/5 1 2 3 4 5 下一页 尾页 |
