Figure 9 shows a simple selfbiasing common source amplifier; RV1 is used to set a quiescent 5V6 across R3. The RV1-R2 biasing network is AC-decoupled via C2, and the circuit gives a voltage gain of 21dB (= x12), and has a ±3dB frequency response that spans 15Hz to 250kHz and an input impedance of 2M2 shunted by 50pF. (This high shunt value is due to Miller feedback, which multiplies the JFET’s effective gate-to-drain capacitance by the circuit’s x12 Av value.)

請(qǐng)問那些下劃線的部分怎么理解,如shunted by 50pF等;特別是a voltage gain of 21dB (= x12);a ±3dB frequency response that spans 15Hz to 250kHz的計(jì)算.謝謝!!!
1145195188.doc