光電放大器：Photocell Amplifiers

Amplifiers for photoconductive, photodiode and photovoltaic cells are shown in Figures 14, 15, 16 respectively. All photogenerators display some voltage dependence of both speed and linearity. It is obvious that the current through a photoconductive cell will not display strict proportionality to incident light if the cell terminal voltage is allowed to vary with cell conductance. Somewhat less obvious is the fact that photodiode leakage and photovoltaic cell internal losses are also functions of terminal voltage.
The current-to-voltage converter neatly sidesteps gross linearity problems by fixing a constant terminal voltage, zero in the case of photovoltaic cells and a fixed bias voltage in the case of photoconductors or photodiodes.
Photodetector speed is optimized by operating into a fixed low load impedance. Currently available photovoltaic detectors show response times in the microsecond range at zero load impedance and photoconductors, even though slow, are materially faster at low load resistances. The feedback resistance, R1, is dependent on cell sensitivity and should be chosen for either maximum dynamic range or for a desired scale factor. R2 is elective: in the case of photovoltaic cells or of photodiodes, it is not required in the case of photoconductive cells, it should be chosen to minimize bias current error over the operating range.

光電放大器用于放大由光電導(dǎo)、光電二極管和光電池所得到的光強(qiáng)度信號(hào)，如圖14、15、16。這些光電傳感器的輸出電壓與線性度和（響應(yīng)）速度有關(guān)。顯然，如果任由光電導(dǎo)電池的端電壓隨其電導(dǎo)變化而變化，那么其輸出電流與入射光強(qiáng)度之間就不會(huì)遵循嚴(yán)格的比例關(guān)系。此外，光電二極管的漏電流和光電池的內(nèi)部損耗也是其端電壓的函數(shù)。
電流——電壓轉(zhuǎn)換電路利用在光電檢測(cè)器的輸出端加上一個(gè)恒定的電壓來(lái)巧妙地解決了整體上的線性度問(wèn)題。對(duì)于光電池來(lái)說(shuō)，這個(gè)電壓為0V；對(duì)于光電導(dǎo)或光電二極管來(lái)說(shuō)，是一個(gè)偏置電壓。

光電檢測(cè)器件，在負(fù)載為適當(dāng)?shù)牡妥杩箷r(shí)，其信號(hào)轉(zhuǎn)換速度將得到優(yōu)化。現(xiàn)行的光電檢測(cè)器在0負(fù)載的情況下，響應(yīng)速度可以達(dá)到毫秒數(shù)量級(jí)，半導(dǎo)體光電器件稍慢，但是在低阻抗負(fù)載的情況下，其速度也會(huì)得到質(zhì)的提高。反饋電阻R1的取值由電池的靈敏度和要求的最大動(dòng)態(tài)范圍，或者需要的電流——電壓轉(zhuǎn)換比例決定。R2分情況選?。涸诠怆姵睾凸怆姸O管時(shí)不需要這個(gè)電阻，在光電導(dǎo)的時(shí)候，電阻的阻值應(yīng)該能使在工作范圍內(nèi)，由OP輸入偏置電流所帶來(lái)的誤差最小。