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Lecture 03
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Lecture 03 Diode circuits Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt topics • Rectifier circuit • Limiting and clamping circuits • Small signal model Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Diode logic gates (ideal diode) Y = A+ B +C Y = ABC Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Example (ideal diode) Assume D1 and D2 are ideal diodes and conducting 10 − I D2 = = 1mA 10k = 5k × ( I + I D ) − 10v ⇒ I = 1mA Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Example (ideal diode) Assuming that D1 and D2 are ideal diodes and conducting 10 − I D2 = = 2mA 5k = 10k × ( I + I D ) − 10v ⇒ I = −1mA Contradictory result Assuming that D1 is off and D2 is on 10 − (−10) I D2 = = 1.33mA 15k VB = 10k × I D − 10v = 3.3v Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt ACỈDC Rectifier Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Rectifier parameters: • Crest factor (C.F.) • Form factor (F.F.) • Ripple factor (R.F.) Vmax C F = Vrms Vrms F F = Vaverage R.F = Vripple − rms T Vaverage = ∫ Vo (t )dt T T Vrms = V o (t )dt ∫ T Root-mean-square Vaverage Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Vaverage Vrms ∫ π ∫ π 0 = T ∫ T v(t )dt = π∫ π T v (t )dt = = ∫ T π Vmax sin θdθ = π 2Vmax v(t ) π Vmax Vmax ∫0 V max sin θdθ = 2 π π sin θdθ = − cos θ = sin θdθ = ∫ π π − cos 2θ dθ = 2 Full-wave rectifier Vaverage = Vrms Half-wave rectifier 2Vmax Vaverage = π Vmax = Vrms Vmax π Vmax = Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Using ideal model Half-wave rectifier Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Using piecewise-linear model Transfer curve R R vo = vs − VD R + rD R + rD vs PIV (peak inverse voltage) = vs 10 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt iD = iC + iL = C dvo vo + dt R dvo vo + =0 dt R dvo (t ) vo (t ) =− , vo (0) = V p dt RC C vo (t ) = ke t − RC vo (t ) = V p e , k = Vp t − RC RC >> T V p − Vr = V p e − − T RC Average diode current iD max T RC T ≈ 1− RC Vp T Vr ≈ V p = RC fRC e iD max = I L (1 + 2π 2V p Half wave Average diode current iDav iDav = I L (1 + π 2V p Vr ) next page 15 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com Vr https://fb.com/tailieudientucntt ) Diode on V p − Vr = V p e − T RC − T RC T RC full wave Vp T Vr ≈ V p = RC fRC Δt e ≈ 1− Average diode current iDav V p cos(ωΔt ) = V p − Vr iDav = ⇒ V p [1 − (ωΔt ) ] = V p − Vr Vp 2Vr (ωΔt ) = Vr ⇒ ωΔt = Vp R (1 + π Vp 2Vr ) Maximum diode current iD max Qc = ic Δt = (iDav − I L )Δt ⇒ iDav = I L + Vp Qc CVr = IL + Δt Δt iD max = Vp R (1 + 2π Vp 2Vr 16 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com ) https://fb.com/tailieudientucntt Limiter circuits vs − 12 iD = 100 17 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Basic limiting circuits 18 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt vo example zone A D1 zone B zone C D2 − 5v + 5v vi zone A : D2 off, D1 on 10k 10k (−5v) vi + 10k + 10k 10k + 10k vo = vi − 2.5v vo = zone B : D2 off, D1 off vo = vi zone C : D2 on, D1 off 10k 10k (5v) vi + 10k + 10k 10k + 10k vo = vi + 2.5v vo = 19 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt example Ideal diodes + Vi R D1 − D2 Vy Vx Vo + Vo − Vx Vy Vx Vi Vy zone A : D1 off, D2 on Vi < V y ⇒ Vo = V y zone C : D1 on, D2 off Vi > Vx ⇒ Vo = Vx zone B : D2 off, D1 off Vx > Vi > V y ⇒ Vo = Vi 20 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt example + Vi − Vi >> VA 15k D1 D1on, D2 off + 5k V o 10V − D2 10k 2.5V ⇒ Vo = 10V Vi Vi > VB ⇒ D1on, D2 on Vo = V (10 // ) i 15 + (10 // ) = 11 + (2Vi + 67.5) (15 // ) 10 + (15 // ) + 10 (10 // 15 ) + (10 // 15 ) (2VB + 67.5) 11 Vo = 10V = (2VA + 67.5) 11 21 Microelectronic Circuit by Vo = 7.5V = meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt DC restoration (clamping circuit) DC restoration with load 22 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Voltage doubler D1 on D2 off D1 off D2 on D1 off D2 on D1 off D2 off 23 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Voltage doubler + + Vm Vm − − + Vm − + + − + Vm Vm − Vm + Vm − − + + Vm − Vm − 24 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt Voltage doubler + Vm − + Vm − + 2Vm + Vm − − + 2Vm + Vm + + Vm − Vm − − − + 2Vm + Vm − + 2Vm − + Vm − − + 2Vm − + + Vm − Vm − + 2Vm − + 2Vm − + 2Vm 25 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com − https://fb.com/tailieudientucntt Operating point (DC analysis) I D = I se VD nVT VD = VDD − RI D 26 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt 27 Microelectronic Circuit by meiling CHEN CuuDuongThanCong.com https://fb.com/tailieudientucntt small signal analysis (AC analysis) I D = I se VD nVT vD = VD + vd (t ) iD = I s e vD nVT iD = I D e = I se (VD + vd ( t )) nVT = I se VD nVT e vd ( t ) nVT vd ( t ) nVT vd (t ) small signal