Op-amp Varieties

Precision Diode

精密二极管

Putting a diode in the feedback path produces a diode which gives virtually zero output for half a cycle and a gain of unity for the other half cycle. It can therefore rectify signals which are smaller than a diode drop. This device would usually be followed by a voltage follower.

将二极管置于反馈路径中，会产生一个二极管，其在半个周期内几乎不产生输出，而在另一个半周期内增益为1。因此，它能够整流幅度小于二极管压降的信号。这种器件通常会随后接一个电压跟随器。

The high frequency response of this device is limited by the slew rate of the op-amp used. Distortion can occur if the op-amp swings to its negative supply voltage and can't get back fast enough. In this case the output will stay at zero too long, distorting the wave.

该设备的高频响应受所用运算放大器的 slew rate 限制。如果运算放大器 swings 到负电源电压并无法及时恢复，就会产生失真。在这种情况下，输出将长时间保持在零，导致波形失真。

Rules application

规则应用

High-frequency modification

高频修正

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	Precision diode 精密二极管
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Rule Application: Precision Diode

规则应用：精密二极管

This can be considered to be a non-inverting amplifier with a diode in the feedback path. When the input goes negative, the output of the op-amp goes to the negative supply so that no current flows and the output is clamped to zero. When the signal goes positive the diode conducts to obey the current rule and the output tracks the input.

这可以被视为一个非反相放大器，其中反馈路径中有一个二极管。当输入信号为负时，运放的输出会降至负电源，使得没有电流流过，输出被钳位到零。当信号为正时，二极管导通以遵循电流规则，输出跟随输入信号。

Note that this is an example where the voltage rule is broken on the non-conducting half cycle. The gain is very high because of the reversed diode, but it can only drive the op-amp to the negative supply and cannot make the inputs equal in voltage.

需要注意的是，这是一个电压规则在非导电半周期中被打破的例子。由于反向二极管，增益非常高，但它只能将运算放大器推到负电源，无法使输入电压相等。

High Frequency Precision Diode

高频精度二极管

This high frequency version of the precision diode relieves the slew rate limitations by preventing the op-amp from swinging to its negative supply voltage. This device would usually be followed by a voltage follower.

这种高频版本的精密二极管通过防止运算放大器 swings 到其负电源电压，从而克服了斜率限制。该器件通常随后由电压跟随器接续。