同相放大器-The Non-Inverting Amplif

Figure 2 shows a high input impedance non-inverting circuit. This circuit gives a closed-loop gain equal to the ratio of the sum of R1 and R2 to R1 and a closed-loop 3 dB bandwidth equal to the amplifier unity-gain frequency divided by the closed-loop gain. The primary differences between this connection and the inverting circuit are that the output is not inverted and that the input impedance is very high and is equal to the differential input impedance multiplied by loop gain. (Open loop gain/Closed loop gain.) In DC coupled applications, input impedance is not as important as input current and its voltage drop across the source resistance. Applications cautions are the same for this amplifier as for the inverting amplifier with one exception. The amplifier output will go into saturation if the input is allowed to float. This may be important if the amplifier must be switched from source to source. The compensation trade off discussed for he inverting amplifier is also valid for this connection.

圖2給出了一個(gè)高輸入阻抗，同相放大器電路的電路。其閉環(huán)放大倍數(shù)為（R1+R2）/R1，其閉環(huán)3dB帶寬為其單位增益帶寬除以其閉環(huán)增益。和反相電路相比，其最大的不同點(diǎn)在于，其輸出信號(hào)和輸入信號(hào)是同相的，其輸入阻抗也是相當(dāng)高的，為OP差模輸入阻抗與環(huán)路增益的乘積（環(huán)路增益為：開(kāi)環(huán)增益/閉環(huán)增益）。在直流耦合情況下，輸入阻抗對(duì)于OP電路的影響作用比起輸入電流，主要是由于其在信號(hào)源內(nèi)阻上所帶來(lái)的壓降來(lái)說(shuō)，是在次要地位的。對(duì)于本電路的應(yīng)用注意事項(xiàng)，除了一點(diǎn)之外均和反相放大器相同：在輸入端懸浮的狀態(tài)下，本電路的輸出可能飽和。這點(diǎn)在要求OP輸出電壓范圍能夠達(dá)到電源電壓范圍的時(shí)候很重要。對(duì)補(bǔ)償?shù)挠懻摵头聪喾糯笃飨嗤?/font>