本帖最后由 Analog921 于 2009-11-14 12:45 编辑
出现这种情况一般有几种原因：
1、输出波形上升沿太快了，在几个纳秒左右甚至ps级别，阻抗不匹配，造成了反射,但是楼主用的芯片几乎可以不考虑这个问题了，估计上升时间很长了。
2、输出端带了容性负载，增加了pole，减小了phase margin 造成OPAMP向振荡的边缘崩溃中～～～，可以用补偿的办法来解决这个问题。
3、似乎还有就是片子本身的特性了（参看datasheet是由于该CMOS OP的输入电容较大造成的）
难道楼主使用芯片的时候不会去阅读datasheet？
在其datasheet 的P17,FIGURE49 1V-STEP就有说明：
The TLC083 with a 1-V step response has an 80% overshoot with a natural frequency of 3.5 MHz when
configured as a unity gain buffer and with a 10-kW feedback resistor. By adding a 10-pF capacitor in parallel with
the feedback resistor, the overshoot is reduced to 40% and eliminates the natural frequency, resulting in a much
faster settling time (see Figure 49).
从datsheet来看这个片子本身的阶跃响应就是很差的～
至于为什么
其datasheet上面有，楼主没有贴出电路图来，我不晓得其具体的单位增益的反馈参数是多少，但是可以参考一下其datasheet：
The TLC08x is a family of high-speed low-noise CMOS input operational amplifiers that has an input
capacitance on the order of 20 pF. Any resistor used in the feedback path adds a pole in the transfer function
equivalent to the input capacitance multiplied by the combination of source resistance and feedback resistance.
For example, a gain of –10, a source resistance of 1 kW, and a feedback resistance of 10 kW add an additional
pole at approximately 8 MHz. This is more apparent with CMOS amplifiers than bipolar amplifiers due to their
greater input capacitance.
This is of little consequence on slower CMOS amplifiers, as this pole normally occurs at frequencies above their
unity-gain bandwidth. However, the TLC08x with its 10-MHz bandwidth means that this pole normally occurs at
frequencies where there is on the order of 5-dB gain left and the phase shift adds considerably.
The effect of this pole is the strongest with large feedback resistances at small closed loop gains. As the
feedback resistance is increased, the gain peaking increases at a lower frequency and the 180° phase shift
crossover point also moves down in frequency, decreasing the phase margin.
For the TLC08x, the maximum feedback resistor recommended is 5 kW; larger resistances can be used but a
c apacitor in parallel with the feedback resistor is recommended to counter the effects of the input capacitance pole.
所以说在提问以前请一定要看看datasheet～～～
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楼主
