Bias Circuit

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Unit 5. Common-Source Amplifier Stage Two types of common-source amplifiers will be investigated in lab projects. One is with the source grounded and the other is with a current-source bias (dual power supply). In Units 5.1 and 5.2 we discuss various aspects of the common-source stage with grounded source, in Unit 5.3 we take up circuit-linearity considerations, and in Unit 5.4 we cover the basics of the dualpower-supply amplifier. Both amplifiers are based on the PMOS, as in the projects. The first two units are mostly a review of the basic amplifier as presented in previous units, to reinforce the basic concepts. The PMOS replaces the NMOS (Units 2 and 4) in this unit, to provide familiarity with the opposite polarity in bias considerations and to illustrate that the linear model applies in the same manner for both transistor types.
5.1 DC (<strong>Bias</strong>) <strong>Circuit</strong> Dc circuits for the grounded-source amplifier are shown in Fig. 5.1 (PMOS). The circuit in (a) is based on a single power supply, and the gate bias is obtained with a resistor voltage-divider network. The circuit in (b) is for a laboratory project amplifier. Both VGG and VSS are negative, since the source is at ground. There is no voltage drop across RG since there is negligible gate current. RG is necessary only to prevent shorting the input signal, Vi. The bias current ID for a given applied VSG will respond according to (3.8), which is ID = kp (VSG – Vtpo) 2 (1 + λpVSD) Figure 5.1. Basic PMOS common-source amplifiers. Single-powersupply amplifier (a) and laboratory amplifier (b) with VSG (= VGG) and VSS controlled by DAQ output channels. Note that either end of the circuit of (a) can be at ground. The two circuits are equivalent, as VGG and RG of Fig. 5.1b are the Thévenin equivalent of the bias network of the Fig. 5.1(a). In the project on the amplifier, they are actually a voltage and a resistor. This is not a bias-stable circuit, as a slight change in VSG or the transistor parameters can result in a significant change in ID. The dual-power-supply circuit of Unit 5.4 is considerably better in this respect.
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Copyright Library of Congress Catal
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National Improvements | Virtual Ins
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formulations, the results from Math
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Hardware and Software Requirements
Page 9 and 10: Chan0_out Pin 21 Chan0_in Pin 68 Gn
Page 11 and 12: LabVIEW VI Libraries and Project an
Page 13 and 14: 1.1 Resistor Voltage Divider and MO
Page 15 and 16: 1.3 Frequency Response of the Ampli
Page 17 and 18: At f = flo, . This, by definition,
Page 19 and 20: 1.5 Exercises and Projects Project
Page 21 and 22: 2.1 BJT and MOSFET Schematic Symbol
Page 23 and 24: 2.2 Fundamentals of Signal Amplific
Page 25 and 26: 2.3 Basic NMOS Common-Source Amplif
Page 27 and 28: Using (2.4), (2.5), (2.9), and (2.1
Page 31 and 32: Unit 3. Characterization of MOS Tra
Page 33 and 34: In electronic circuit applications,
Page 35 and 36: The output-characteristic equation
Page 37 and 38: Equation 3.11 From the data measure
Page 39 and 40: The input circuit loop equation (Fi
Page 41 and 42: which leads to the result (3.5), re
Page 46 and 47: Unit 4. Signal Conductance Paramete
Page 48 and 49: 4.2 Transistor Variable Incremental
Page 50 and 51: 4.3 Transconductance Parameter The
Page 52 and 53: 4.4 Body-Effect Transconductance Pa
Page 54 and 55: 4.5 Output Conductance Parameter Th
Page 56 and 57: With a 1 - V drop across RS and a 5
Page 58 and 59: By the nature of the load-line func
Page 62 and 63: 5.2 Amplifier Voltage Gain This dc
Page 64 and 65: etween the drain and source of the
Page 66 and 67: 5.3 Linearity of the Gain of the Co
Page 68 and 69: where av Vds/Vgs and where the appr
Page 70 and 71: is attached directly to the gate. B
Page 72 and 73: 5.5 Design of a Basic Common-Source
Page 74 and 75: = VGSo - Vtno at the high and low e
Page 76 and 77: RG can be selected somewhat arbitra
Page 80 and 81: 6.1 Grounded-Source Amplifier: Coup
Page 82 and 83: and Equation 6.6 Note that the "RC"
Page 84 and 85: 6.4 Load Coupling Capacitor The com
Page 87 and 88: 6.5 Summary of Equations MOSFET cou
Page 89 and 90: Unit 7. MOSFET Source-Follower Buff
Page 91 and 92: 7.2 Source-Follower Voltage Transfe
Page 93 and 94: 7.3 Body Effect and Source-Follower
Page 95 and 96: 7.4 Summary of Equations Threshold
Page 97 and 98: Unit 8. MOSFET Differential Amplifi
Page 99 and 100: 8.2 DC Imbalances In a real transis
Page 101 and 102: 8.3 Signal Voltage Gain of the Idea
Page 103 and 104: 8.4 Effect of the Bias Resistor on
Page 105 and 106: 8.5 Differential Voltage Gain Suppo
Page 107 and 108: 8.7 Voltage Gains Including Transis
Page 109 and 110: 8.7.2 Common-Gate Amplifier Stage T
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with RD1 = RD2 and gm1 = gm2. In th
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It follows that the gain for the in
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8.9 Amplifier Gain with Differentia
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8.11 Summary of Equations Rs = Ris2
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8.12 Exercises and Projects Project
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9.1 Basic Current Source An example
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9.2 Current Source with Source Dege
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If the magnitude of the voltage acr
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Any slight possible difference in
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Unit 10. Common-Source Amplifier wi
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10.2 Signal Voltage Gain The expres
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10.3 Summary of Equations Output dr
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Unit 11. Operational Amplifiers wit
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11.1.1 Voltage Gain of the Noninver
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This expression can be manipulated
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11.3 Operational Amplifier Offset I
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where the approximation usually app
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where Avo is the amplifier gain at
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12.1 Operational Amplifier Integrat
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This demonstrates that for the circ
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with a steady-state value of Vop. A
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Equation 12.25 A good estimate come
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13.1 Combining NMOS and PMOS Circui
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13.3 Stabilization of Signal Gain a
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An estimate of the new output volta
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This produces (9.9) from Ro = Vo/Io
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Equation 13.13 where 13.12 has been
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The open-loop transconductance is G
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Unit 14. Development of a Basic CMO
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14.2 Current-Source Output Resistan
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14.3 Current-Source Load for the Co
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14.4 Current-Source Load for the Di
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the node (exclusive of the separate
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14.5 Two-Stage Amplifier with Curre
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14.6 Output Buffer Stage It is evid
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Suppose that ID6 = 400 µA, W6 = 50
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Av and Ro are calculated once, usin
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Since the source follower of M1 has
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14.9 Summary of Equations CMRR = 1
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Unit A. Communicating with the Circ
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Place AI Acquire Waveform.vi in the
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Click from the Front Panel or Diagr
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Now go to the Diagram (under Menu W
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To complete connections to the term
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Now use the Edit Text Tool to edit
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on the left in the diagram . The Wh
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Figure A.15. Frame of Sequence Stru
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The transition regions are nonabrup
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during the oscilloscope measurement
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Unit B. Characterization of the Bip
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junction diodes, the current is lar
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common to the input and output and
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B.2 Base-Width Dependence on Juncti
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Figure B.8. Diodelike characteristi
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The minus sign comes from having as
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Figure B.10. Circuit for measuring
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B.5 Output Characteristics of BJT i
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After measuring the output characte
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B.6 SPICE Solution for IC versus VC
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B.7 Collector-Emitter Voltage and C
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B.8 DC as a Function of Collector C
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B.10 Summary of Equations Common-em
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Unit C. Common-Emitter Amplifier St
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The equation set above has three un
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The output-resistance parameter, ro
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of βDC as possible. Signal paramet
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Equation C.17 We note that the magn
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C.4 Accuracy of Transistor Gain Mea
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C.5 Effect of Finite Slope of the T
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It follows that for this case, f3dB
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C.7 Common-Emitter Amplifier with A
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Equation C.41 where IC IC(VCE), tha
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Applied voltage Vo sums up to Equat
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C.7.3 DC (Bias) of the NPN - PNP Am
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where Equation C.58 and Equation C.
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Equation C.67 The result is signifi
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The following form of the result pr
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This is equivalent to a unity-gain
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C.11 Summary of Circuit Equations B
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C.12 Exercises and Projects Project
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P1.1 Resistor Voltage-Divider Measu
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• Place AO Update Channel.vi in F
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• (Optional) To install the circu
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Procedure • Set your value of RG2
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• In the Diagram, we will add Get
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P1.4 Resistor Voltage Divider with
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• Now move the capacitor C2 = C1
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P2.1 NMOS Common-Source Circuit wit
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• In the Diagram (below), place,
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P2.2 NMOS Common-Source Amplifier w
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P2.3 Amplifier with Signal and Gain
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• Connect to FG1Chan.vi, the vari
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P3.1 SPICE Parameters and Pin Diagr
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P3.3 PMOS Transistor Use pins 6 (ga
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Procedure • Run PMOSlinear.vi and
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Procedure • Run PMOSparsub.vi wit
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Procedure • Run PMOSparam.vi to r
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Active Region Procedure • Install
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Laboratory Project 4. Characterizat
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P4.2 NMOS Transistor Use CD4007 pin
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P4.4 NMOS Parameters from the Trans
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P4.5 NMOS Lambda from the Transfer
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P4.6 NMOS Gamma SubVI Components No
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• Set RS. With NMOSgamsub.vi open
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• A file can be obtained from the
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P5.1 SPICE Equations and Pin Diagra
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P5.3 Amplifier Gain at One Bias Cur
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P5.4 Amplifier Gain versus Bias Cur
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Laboratory Project 6. PMOS Common-
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P6.2 SPICE PMOS and Circuit Equatio
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P6.4 Amplifier Gain LabVIEW Computa
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P6.5 Amplifier Frequency Response P
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P7.1 Chip Diagram and SPICE Equatio
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P7.3 Amplifier Gain at Optimum Bias
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P7.4 Optimum Bias Stability Test
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P7.5 Amplifier Frequency Response P
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Laboratory Project 8. NMOS Source-
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P8.2 Source-Follower DC Evaluation
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available for the next VI. It is us
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Laboratory Project 9. MOSFET Differ
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P9.2 DC Evaluation of the Single-Po
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P9.3 Determination of the PMOS Para
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Gains will be obtained from the gra
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• Run SweepSim.vi to obtain the d
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Laboratory Project 10. Current Mirr
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P10.2 Evaluation of the Current-Sou
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P10.4 Evaluation of the Bias Setup
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Laboratory Project 11. Operational
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P11.2 Bias Circuit Setup 1 Offset N
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P11.3 Opamp Offset Voltage Componen
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P11.4 Evaluation of the Bias Balanc
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VOH • Reset the Chan0_out Range,
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P11.6 Evaluation of the Gain with S
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P11.7 Determination of the Opamp Fr
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Laboratory Project 12. Operational
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P12.2 Opamp Integrator Components R
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Procedure • Turn off the power su
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Laboratory Project A. Communicating
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PA.2 Sending and Receiving Voltages
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Bipolar TABLE PA.2 0 to +5V 1.22 mV
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PA.5 Observing the Oscilloscope Out
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of the DAC. The steps are 2.44 mV f
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• The example here illustrates th
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Laboratory Project B. Characterizat
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PB.2 SPICE Equations SPICE Equation
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parameters nF and IS. • Connect C
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PB.4 DC versus the Collector Curren
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• Now open VI, IC_VCE.vi. Set the
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Laboratory Project C1. NPN Common-
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PC.2 DC Circuit Setup and Parameter
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PC.3 Amplifier Gain at One Bias Cur
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PC.4 Amplifier Gain versus Bias Cur
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• Run FreqResp.vi. Verify that in
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PC.6 SPICE Equations and Pin Diagra
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• Determine the value of VAF spec
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• Set the Run Mode switch to Set
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• Now reset VCC(init) and VBB(ini
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Bias Circuit

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