The guard amplifier is a unity-gain amplifier with very high input impedance. 保護放大器是一個具有非常高輸入阻抗的單位增益放大器。
To gain further bisymmetric baseband signals, the proposed transconductance stage is formed with a cross-coupled type. 之後經過可變增益放大器將升頻后之訊號放大到功率放大器所要求之強度。