MT19301 – ANOLOG DEVICES
AND CIRCUITS
UNIT 5 –VOLTAGE REGULATOR IC’S
,Voltage Regulator
• One of the most widely used electronic circuitry in any device.
• A regulated voltage (without fluctuations & noise levels) is very
important for the smooth functioning of many digital electronic devices.
• Function – to provide a stable dc voltage for powering other electronic
circuits.
• Capable of producing substantial output current.
,Classification
• Series Regulator – Uses a power transistor connected in series b/w the unregulated dc input and load.
– Output voltage – controlled by continuous voltage drop taking place across the series pass transistor
– Transistor conducts in linear or active region, called as Linear Regulators.
– Linear Regulators – Fixed or variable output voltage (Positive or negative).
• Switching Regulator – Operate the power transistor as a high frequency ON/OFF Switch, doesn’t conduct cu
– Gives improved efficiency over series regulator.
, Series Op-Amp Regulator
• An electronic circuit provides a stable dc voltage independent of the load current, temperature and ac
variations.
• Four Parts: Reference Voltage Circuit, Error Amplifier, Series Pass Transistor, Feedback Network
• Power transistor Q1 in series with unregulated dc voltage Vin and output voltage Vo.
• It absorbs the difference between the two voltages whenever any fluctuation in output voltage Vo occurs.
• Q1 connected as emitter follower – Provides sufficient current gain to drive the load.
• Output voltage – Sampled by R1 – R2 divider network, fed back to (-Ve) terminal of error amplifier.
• Sampled voltage compared with Ref. voltage (Zener Voltage).
• When output voltage increases Vo ↑, then sampled v
βVo = Vo (R2/R1+R2) ↑, which causes amplifier o
reduces IB, which reduces the IE. Hence the out
reduced.
• In other words, Vo’ is applied to base of Q1, which
follower. So, Vo follows Vo’, that is Vo’ reduces, Vo al
AND CIRCUITS
UNIT 5 –VOLTAGE REGULATOR IC’S
,Voltage Regulator
• One of the most widely used electronic circuitry in any device.
• A regulated voltage (without fluctuations & noise levels) is very
important for the smooth functioning of many digital electronic devices.
• Function – to provide a stable dc voltage for powering other electronic
circuits.
• Capable of producing substantial output current.
,Classification
• Series Regulator – Uses a power transistor connected in series b/w the unregulated dc input and load.
– Output voltage – controlled by continuous voltage drop taking place across the series pass transistor
– Transistor conducts in linear or active region, called as Linear Regulators.
– Linear Regulators – Fixed or variable output voltage (Positive or negative).
• Switching Regulator – Operate the power transistor as a high frequency ON/OFF Switch, doesn’t conduct cu
– Gives improved efficiency over series regulator.
, Series Op-Amp Regulator
• An electronic circuit provides a stable dc voltage independent of the load current, temperature and ac
variations.
• Four Parts: Reference Voltage Circuit, Error Amplifier, Series Pass Transistor, Feedback Network
• Power transistor Q1 in series with unregulated dc voltage Vin and output voltage Vo.
• It absorbs the difference between the two voltages whenever any fluctuation in output voltage Vo occurs.
• Q1 connected as emitter follower – Provides sufficient current gain to drive the load.
• Output voltage – Sampled by R1 – R2 divider network, fed back to (-Ve) terminal of error amplifier.
• Sampled voltage compared with Ref. voltage (Zener Voltage).
• When output voltage increases Vo ↑, then sampled v
βVo = Vo (R2/R1+R2) ↑, which causes amplifier o
reduces IB, which reduces the IE. Hence the out
reduced.
• In other words, Vo’ is applied to base of Q1, which
follower. So, Vo follows Vo’, that is Vo’ reduces, Vo al
