Learn Analog Circuits with Zundamon

YouTube playlist (English videos)

Episodes

1. Episode 1

   How Transistors Work: MOSFET vs BJT and CMOS

   Join Zundamon and Shikoku Metan to learn how transistors work, from the MOSFET channel to the CMOS inverter.

   1. Intro: my course is in danger!
   2. Transistors in modern ICs: CMOS
   3. BJT vs. MOSFET
   4. MOSFET symbols and terminals
   5. Why current flows: the channel in cross-section
   6. I_D–V_GS characteristics and the square law
   7. Inside the current equation: μ_nC_ox and W/L
   8. The subthreshold region
   9. I_D–V_DS characteristics and the linear region
   10. Pinch-off
   11. Saturation and the voltage-controlled current source
   12. Summary: three operating regions
   13. PMOS and the CMOS inverter
   14. Next time
2. Episode 2

   Channel-Length Modulation, Output Resistance and Body Effect

   Why does a MOSFET's current keep increasing in saturation? Explore channel-length modulation, output resistance, and the body effect.

   1. Intro: a lab graph that slopes upward
   2. Measuring the slope
   3. The cause: the pinch-off point moves
   4. The equation: I_D ≈ ½KV_ov²(1 + λV_DS)
   5. Output resistance r_o and the equivalent circuit
   6. Early voltage V_A
   7. Channel length L and λ
   8. Why r_o matters: intrinsic gain g_m·r_o
   9. Body effect
   10. Summary
3. Episode 3

   Transconductance and the Common-Source Amplifier

   The key to amplifying a signal with a MOSFET is transconductance g_m and the small-signal model.

   1. Intro: a larger input distorts the waveform
   2. Bias point and small signals (uppercase and lowercase notation)
   3. Why use both large-signal and small-signal analysis?
   4. Defining g_m: the tangent slope
   5. g_m = K·V_ov=2·I_D/V_ov in saturation
   6. Numerical example and the small-signal condition
   7. The NMOS small-signal equivalent circuit: four steps
   8. Intrinsic gain g_m·r_o
   9. Common-source amplifier: load line and transfer curve
   10. Small-signal circuit and A_v = −g_m(R_D∥r_o)
   11. Output swing limits
   12. What each analysis reveals
   13. Solving small-signal circuits efficiently: R_in, R_out, and G_m
   14. Frequency response and SPICE AC analysis
   15. Summary
4. Episode 4

   Current Mirrors and Active Loads

   Increasing the load resistor stopped the amplifier from working. Learn how current mirrors and active loads provide high gain while preserving the bias current.

   1. Intro: why did a larger R_D stop amplification?
   2. Review: increasing R_D
   3. Using a current source as the load
   4. Creating a current source with a diode connection
   5. The current mirror
   6. Mirror error from r_o and the saturation condition
   7. A closer look at PMOS
   8. The common-source amplifier with an active load
   9. Small-signal equivalent circuit and A_v
   10. Intrinsic gain and a numerical example
   11. Setting the operating point
   12. Summary
5. Episode 5

   Source Followers and Common-Gate Amplifiers

   Connecting a load can drastically reduce gain. Explore the source follower and common-gate stage, and compare the three basic amplifier configurations.

   1. Intro: the load makes the gain collapse
   2. Three ways to connect a MOSFET
   3. Source follower: large-signal behavior
   4. Source follower: small-signal gain and body effect
   5. Source-follower output resistance
   6. The role of a buffer
   7. The common-gate stage
   8. Comparing the three basic amplifiers
   9. Summary
6. Episode 6

   Cascodes: Raising Output Resistance

   How can we get more gain from the same 1.8 V supply? Stack transistors to build a cascode, then examine the headroom tradeoff.

   1. Intro: more gain from a 1.8 V supply
   2. Review: the intrinsic-gain limit
   3. The cascode circuit
   4. Why output resistance increases
   5. Deriving output resistance with a small-signal model
   6. Comparing output current–voltage curves
   7. The cascode current mirror
   8. The cascode amplifier
   9. The cost: voltage headroom
   10. Summary
7. Episode 7

   Differential Pairs and Active Loads

   Amplifying a microphone signal also amplifies its noise. Explore how a differential pair amplifies the difference between two inputs and rejects common-mode interference.

   1. Intro: microphone noise that will not go away
   2. Why differential signals?
   3. The differential-pair circuit
   4. Large-signal behavior
   5. Differential and common-mode signals
   6. Differential half-circuit and gain
   7. Common-mode half-circuit and gain
   8. Common-mode rejection ratio (CMRR)
   9. The active-load differential pair
   10. Summary
8. Episode 8

   Op-Amps: Two Rules for Amplifiers and Integrators

   Build a ten-times amplifier with an op-amp. Learn negative feedback and the two ideal rules, then derive the follower, non-inverting amplifier, inverting amplifier, and integrator. Look inside a CMOS op-amp to see how finite gain, loading, bandwidth, output swing, and offset limit real circuits.

   1. Introduction: build a ten-times amplifier
   2. What is an op-amp? Amplifying the input difference
   3. Negative feedback and the virtual short: two rules
   4. Voltage followers and non-inverting amplifiers
   5. Inverting amplifiers and integrators
   6. Inside CMOS: from a differential pair to two stages
   7. Bandwidth, output swing, and offset limits
   8. Summary: using an op-amp and understanding its internals
9. Episode 9

   雑音の基礎: 小さな信号は何に埋もれる？Japanese only

10. Episode 10

    周波数特性①: MOSFETの容量とミラー効果Japanese only

11. Episode 11

    周波数特性②: 極・零点と多段回路Japanese only

12. Episode 12

    設計: SKY130で2段CMOSオペアンプを作るJapanese only

Side topics

Short detours into semiconductor topics, readable at any point in the series (Japanese only for now).

1. Side topic #1

   FinFETからGAAへ: 2 nmの中で何が変わった？Japanese only

2. Side topic #2

   AI半導体なのにメモリ会社が大儲け？ メモリウォールとHBMJapanese only