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GATE analog circuits: 5 practice questions with answers

By the PrepMatic team · Updated 9 Oct 2026 · 4 min read

Analog Circuits is a full section of the GATE EC paper, and EE covers similar ground under Analog and Digital Electronics. The questions are numerical: find a bias current, an output voltage or a gain, with ideal models and round numbers. The method is the same each time. Write the governing equation, substitute carefully, and check units. The five original questions below practise exactly that.

What GATE tests in analog circuits

The GATE 2027 EC syllabus has Analog Circuits and Electronic Devices as separate sections, and EE has an Analog and Digital Electronics section. Both were revised for 2027, so confirm the lists on the official syllabus page. The standard content is diode circuits, BJT and MOSFET biasing and small-signal models, single-stage and multistage amplifiers, op-amp circuits, feedback, oscillators and power amplifiers.

Typical questions ask for a DC operating point, a gain, an output voltage, a frequency or a stability condition. The real paper has MCQ, MSQ and NAT questions, and NAT answers need the right number of decimals. All five below are MCQ.

Practice questions

Question 1

An ideal op-amp is connected as an inverting summing amplifier with feedback resistor Rf = 10 kΩ and input resistors R1 = 5 kΩ and R2 = 10 kΩ. The inputs are V1 = 1 V through R1 and V2 = 2 V through R2. The output voltage is:

• A. −4 V
• B. −2 V
• C. +2 V
• D. +4 V

Question 2

A BJT amplifier uses voltage-divider bias with VCC = 12 V, R1 = 40 kΩ from VCC to the base, R2 = 10 kΩ from the base to ground and RE = 1 kΩ. Take VBE = 0.7 V and assume the base current is negligible. The collector current is approximately:

• A. 1.2 mA
• B. 1.5 mA
• C. 1.7 mA
• D. 2.4 mA

Question 3

An n-channel MOSFET in saturation has ID = (1/2) kn (VGS − Vt)², with kn = 2 mA/V² and Vt = 1 V. At VGS = 3 V the transconductance gm is:

• A. 1 mS
• B. 2 mS
• C. 3 mS
• D. 4 mS

Question 4

An amplifier has an open-loop gain A = 1000, and negative feedback with feedback factor β = 0.01 is applied. The closed-loop gain is approximately:

• A. 10
• B. 90.9
• C. 100
• D. 909

Question 5

A Zener regulator uses a 15 V supply, a series resistor of 200 Ω and a 9.1 V Zener diode in parallel with a 1 kΩ load. The Zener is in breakdown. The current through the Zener diode is:

• A. 38.6 mA
• B. 29.5 mA
• C. 20.4 mA
• D. 9.1 mA

Answers and explanations

1. A. For an inverting summer, Vout = −Rf (V1/R1 + V2/R2) = −10 kΩ × (1 V / 5 kΩ + 2 V / 10 kΩ) = −10 kΩ × (0.2 mA + 0.2 mA) = −4 V. Each input source contributes its current into the summing node, and the virtual ground makes them add.
2. C. The divider gives VB = 12 × 10 / (40 + 10) = 2.4 V. The emitter voltage is 2.4 − 0.7 = 1.7 V, so IE = 1.7 V / 1 kΩ = 1.7 mA. With negligible base current, IC ≈ IE = 1.7 mA.
3. D. The overdrive is VGS − Vt = 2 V, and gm = ∂ID/∂VGS = kn (VGS − Vt) = 2 mA/V² × 2 V = 4 mS. Equivalent forms give the same answer: ID = 0.5 × 2 × 4 = 4 mA, and gm = 2 ID / (VGS − Vt) = 8 mA / 2 V = 4 mS.
4. B. The closed-loop gain is Af = A / (1 + Aβ) = 1000 / (1 + 10) = 90.9. The loop gain Aβ is 10, so the gain is cut by a factor of 11, and in return its sensitivity to changes in A drops by the same factor.
5. C. The series resistor carries (15 − 9.1) / 200 Ω = 29.5 mA. The load takes 9.1 V / 1 kΩ = 9.1 mA. The Zener carries the difference: 29.5 − 9.1 = 20.4 mA. Option B is the total current, which ignores the load.

How to prepare analog circuits

• Start with DC analysis. Almost every amplifier question needs the operating point first, whether the transistor is a BJT or a MOSFET. Learn to check the region of operation (active or saturation) after you compute.
• Memorise the small-signal parameters: gm = IC / VT for a BJT (VT ≈ 26 mV at room temperature), rπ = β / gm, gm = kn (VGS − Vt) for a MOSFET, and the voltage gains of the common-emitter, common-collector, common-source and common-drain stages.
• Use the virtual-short idea for op-amp circuits. Write KCL at the inverting node, then recognise the standard forms: inverting, non-inverting, summing, difference, integrator, differentiator and instrumentation amplifier.
• Learn the four feedback topologies and what each does to input and output impedance, plus the Barkhausen condition for oscillators (loop gain of unity with zero net phase).
• Revise the frequency response basics: poles, the gain-bandwidth product, and the Miller effect.
• Draw the circuit again in your own style before solving. Mislabelled resistors cause most of the lost marks here.

Analog circuits links to digital circuits for EC in the same paper, and to communications. The GATE ECE preparation guide and GATE electrical preparation guide place this topic in the subject order for each branch.

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