전자 회로 1Lecture 8 (MOSFET-III)

2009. 05.임한조

아주대학교 전자공학부hanjolim@ajou.ac.kr

이 강의 노트는 전자공학부 곽노준 교수께서 08.03 에 작성한 것으로 노트제공에 감사드림 .

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Single-stage MOS Amplifier - Biasing

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The Common-Source (CS) Amp.

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The CS with a Source Resistance

Source 쪽에 저항이 있으면 T-model 이 편함

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The Common-Gate (CG) Amp.

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- Non-inverting- Low input resistance- Unity current gain (current follower)- 좋은 주파수 특성 (high freq. response 가 좋음 )

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The Common-Drain (Source Follower)

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- Non-inverting- high input resistance- Low output resistance- Unity voltage gain (voltage follower)

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Summary: Single-stage MOS AMP.

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Internal Capacitance (MOSFET)

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MOS Gate Capacitance

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MOS Junction Capacitance

Internal capacitance 크기 : fF (10-15 F) to pF (10-12 F) (see Ex. 4.36)

Cf.) Coupling cap. ~ 10-6 F

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MOSFET High Frequency Model

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MOS Internal Capacitances (high freq model)

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High Freq. Small Signal Model

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MOSFET Unity Gain Freq. (fT)

* fT ~= 100MHz (old tech.) / several GHz (new tech.)

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The CMOS Digital Logic Inverter

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The depletion type MOSFET

Inversion layer 를 미리 만들어 놓음 . NMOS 인 경우 : Gate 밑에 n 형으로 살짝 doping Vt < 0: channel 이 없어지는 voltage VGS = 0 일 때도 VDS > 0 이면 전류가 흐름

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전류 - 전압 특성 (depletion type MOS)

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비교 (Depletion vs. Enhancement)