Figure 6. Using two resistors (R4 and R5) in parallel with the original circuit, to increase bandwidth 100 times over Figures 1 and 2.
Using a Parallel Resistor String to Lower the Circuit ImpedanceThe circuit of Figure 6, adds a parallel resistor string to that of Figure 1 (note the use of the model for a digital pot introduced in Figure 2). This parallel string lowers the impedance of the circuit (thus improving its bandwidth), and it also does double duty by setting the gain of the circuit and limiting the attenuation caused by the digital pot as it swings from 0-Code to Full-Scale Code.
Setting the gain of the potentiometer circuit and limiting its adjustment range by using parallel devices (R4 and R5), instead of by simply src="/data/attachment/portal/201007/ET33815201007230417397.gif" top? part of the circuit.?>
Figure 7. Simplifying the resistors in the "top" part of the circuit.
In Figure 8, the resistors in the bottom part of the circuit are combined using the equation in that figure. Note that since R5 is in parallel with R3 and R2bottom, it too lowers the circuit impedance. It is this lowered circuit impedance that gives us the dramatic bandwidth gains which we're searching for.
Figure 8. Simplifying the resistors in the "bottom" part of the circuit.
Figure 9 combines both simplifications from the previous figures, and gives the equations for the VOUT/VIN transfer function. It should be clear from this figure that by lowering the impedance of the circuit (Rtop is lower than R1 + R2top, Rbottom is lower impedance than R2bottom + R3), the bandwidth of the circuit has increased.
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
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