Overview
This lecture introduces the focus of the Analog VLSI Design course: designing amplifiers that achieve power amplification, rather than just voltage or current amplification.
Introduction to Amplifiers
- Amplification refers to increasing an electrical quantity, commonly voltage or current.
- A voltage amplifier increases the voltage across a load (V_out = A_V × V_in, where A_V > 1).
- A current amplifier increases the current through a load (I_out = A_I × I_in, where A_I > 1).
Focus of the Course: Power Amplification
- The course aims to design a block (amplifier) that delivers more output power to the load than the input power from the source.
- Power amplification means P_out = A_P × P_in, with A_P > 1.
- Power amplification is important for applications like microphones and loudspeakers, where output power must exceed input power.
Example: Transformer as an Amplifier
- An ideal transformer can step up voltage (V_naught = n × V_1) and transform the load resistance (effective R_L at input = R_L / n²).
- Voltage amplification occurs if R_L » n²R_S, leading to V_0 ≈ n × V_in.
- However, a transformer cannot achieve power amplification; it only transforms voltage and current without increasing total power.
Key Terms & Definitions
- Voltage Amplifier — Device that increases voltage across a load (V_out > V_in).
- Current Amplifier — Device that increases current through a load (I_out > I_in).
- Power Amplifier — Device that increases the power delivered to a load (P_out > P_in).
- Transformer — Device that can step up/down voltage and current via a turns ratio but cannot amplify power.
- Turns Ratio (n) — Ratio of secondary to primary windings in a transformer, determines voltage transformation.
Action Items / Next Steps
- Calculate P_out / P_in for the transformer example: assume input voltage V_in = V_B sin(ω₀t) and determine if power amplification occurs.