1) Consider the difference amplifier shown in Figure 1 and in example 2.6 in Sedra and Smith. Design the amplifier with a differential gain of about 30 with R₁ between 4 and 6 k.

2) Consider the instrumentation amplifier shown in Figure 3 and in example 2.7 in Sedra and Smith. Design the amplifier with a total differential gain of about 600, that is V₀ = 600(V₁-V₂) (the differential gain of 30 is part of this).

3) Consider Wheatstone bridge in Figure 4 (ignore R₁ and R₂ initially). This simple 4 resistor circuit has been used for many years to convert a change in small resistance to a proportional change in output voltage.

• Assume that the resistance of the strain gauge is equal to R. Show that V₀ is 0.0 V. Hint: each side of the bridge is a simple voltage divider.
• Find V₀ if the resistance of the strain gauge increased by 0.1 %.
• Find V₀ if the resistance of the strain gauge decreased by 0.1 %.
• How close are these values to the approximation, V₀ = ( Delta R /R ) V⁺ / 4 ?
• The resistance of the strain gauge is close to 120 ohms. The other resistors, R are about 121 ohms. R₁ and R₂ are used to balance the bridge (set V₀ to 0.00 V). If R₁ and R₂ are both 10 K, what is the minimum and maximum of the parallel resistance of that section of the bridge?