5 The circuit diagram of a simple op-amp is shown in Figure 4. Figure 4 5.1 Perform an approximate dc analysis of the circuit to determine the dc currents and voltages everywhere in the circuit assuming the inputs are grounded, β > 1 and |VBE| ≈ 0,7 V. 5.2 Assuming the BJTs have β = 100, determine the differential voltage gain and input resistance, and the output resistance of the op-amp. 5.3 If due to production mismatch BJTQ has β = 120, determine the input bias current IB and input offset current IOS for this op-amp.
![Consider a BJT differential amplifier biased with a Widlar current source, as shown in Figure 4. The transistor parameters are: β = 200, VBE(ON) = 0.7 V (except for Q3 and Q4), VA = ∞ for Q1 and Q2, and VA = 100 V for Q3 and Q4. Reverse saturation current, Is for transistor Q3 and Q4 is given as 1×10−15 A. From analysis, it is determined that I1 = 0.5 mA, la = 400 μA, v1 = v2 = 0 V, VCE2 = 2.7 V and CMRR (dB) = 80 dB Figure 4 a) Calculate the value of resistors R1, R2 and RC. b) Find the amplifier's differential-mode voltage gain (Ad), common-mode voltage gain (ACM) and common-mode output resistance ( Ricm ). [Ricm ≈ (1+β)Rocs where Rocs is the output resistance of the current source ] c) Draw the pnp version for the differential amplifier of Figure 4. Clearly label all resistors and currents.](https://www.doubtrix.com/uploads/editor/6551442834FjRRsYNstK.jpg)
