Dual Input, Balanced Output Difference Amplifier:

Circuit is shown in the figure 1 v₁  and v₂  are the 2 inputs, applied to the bases of Q₁  and Q₂ transistors. The output voltage can be measured between the 2 collectors C₁ and C₂, which are at the same DC potentials.

Fig. 1

A.C. Analysis :

In the earlier topic DC analysis has been done to obtain the operating point of two transistors. To find the voltage gain Ad  and input resistance R_i  of differential amplifier, AC equivalent circuit is drawn by using r-parameters as shown in the figure 2. The DC voltages are reduced to zero and the AC equivalent of CE configuration is used.

Figure 2

As the 2 DC emitter currents are equal. Hence, resistance r'_e1 and r'_e2 are also equal and designated by r'_e . This voltage across each collector resistance is shown 180° out of phase with respect to input voltages v₁ and v₂. This is identical to CE configuration. The polarity of the output voltage is given in Figure. The collector C₂ is supposed to be more positive with respect to the collector C₁ even though both are negative with respect to ground.

Applying KVL in 2 loops 1 & 2.

Substituting the current relations,

Again, supposing R_S1 / b and R_S2 / b are quite small in comparison with R_E and r_e' and thus neglecting these terms,

Solving these 2 equations, i_e1 and i_e2 can be computed.

The output voltage V_O can be given by

V_O = V_C2 - V_C1

= -R_C i_C2 - (-R_C i_C1)

= R_C (i_C1 - i_C2)

= R_C (i_e1 - i_e2)

Substituting i_e1, & i_e2 in above expression

Therefore a differential amplifier amplifies difference between the two input signals. Defining the difference of input signals as v_d  = v₁  - v₂  the voltage gain of dual input balanced output differential amplifier can be given as follows

                                                      (E-2)  

Email based Electronics Devices and circuits assignment help - homework help at Expertsmind

Are you searching Electronics Engineering assignment help expert for help with Dual Input, Balanced Output Difference Amplifier questions?  Dual Input, Balanced Output Difference Amplifier topic is not easier to learn without any external help?  We at www.expertsmind.com offers free lecture notes for Electronics Devices and circuits assignment help and Electronics Devices and circuits homework help. Live tutors are available 24x7 hours for helping students in their Dual Input, Balanced Output Difference Amplifier related problems. We provide step by step Dual Input, Balanced Output Difference Amplifier question's answers with 100% plagiarism free content. We prepare quality content and notes for Dual Input, Balanced Output Difference Amplifier topic under Electronics Devices and circuits theory and study material. These are avail for subscribed users and they can get advantages anytime.

Why Expertsmind for assignment help

1. Higher degree holder and experienced experts network
2. Punctuality and responsibility of work
3. Quality solution with 100% plagiarism free answers
4. Time on Delivery
5. Privacy of information and details
6. Excellence in solving electronics engineering questions in excels and word format.
7. Best tutoring assistance 24x7 hours