# PSpice virtual lab4 - Quiz Sheet 4

Document Sample

```					Name: Administrator                                                       Marks:     20 /20
Lib ID No.: ########

PSpice virtual lab4 – Quiz Sheet 4 (Answers)

Please complete this quiz sheet, independently as far as possible, as you work through
the lab sheet and submit it, anonymously, electronically by the specified deadline to:
http://www.eng.warwick.ac.uk/assignments/.
Also please make sure that you investigate each of the options thoroughly.

1. For ohm.cir verify Ohm’s law at node 2 using some typical results. [1 mark]
 Ohm’s law : V=R I
 Verify V(R2)=V(2)-V(0)=V(2)=R .I(R2) with R2=680
 When Vin=4V : V(2)=3.02V and I(R2)=4.44mA => eval I(R2).R2=3.02V
 When Vin=10V : V(2)=7.56V and I(R2)=11.11mA => eval I(R2).R2=7.56V

1. For vd.cir verify potential divider behavior at node 2 using typical results. [1 mark]
 Potential divider : V2=Vin .R2/(R2+R1)
 Verify V(R2)=V(2)-V(0)=V(2)=Vin .R2/(R2+R1) with R2=1k and R1=6k
 When Vin=14V : V(2)=2V => eval Vin .R2/(R2+R1)=4x1000/(1000+6000)=2V
 When Vin=6V : V(2)=857mV => eval Vin .R2/(R2+R1)=0.857V

Master Document – Do Not Disclose                                                        1
1. For hpf.cir verify the 3dB frequency. [1 mark]
 3dB Freq : f(3dB)=w/(2.pi)=1/(2.pi.RC)
 From graph F(3dB)=1.59kHz => eval 1/(2.pi.RC)=1590

1. For lpf.cir verify the 3dB frequency. [1 mark]
 3dB Freq : f(3dB)=w/(2.pi)=1/(2.pi.RC)
 From graph F(3dB)=159kHz => eval 1/(2.pi.RC)=159x10e3

1. For bpf.cir verify the 3dB corner frequencies. [1 mark]
 Gain band-pass = 19dB
 F(low cut-off) = 1.2kHz          [1kHz to 1.5kHz]
 F(high cut-off) = 19.3kHz        [18kHz to 21kHz]

1. For diode.cir what are the values you obtain for cut-in voltage and the forward
resistance? [2 marks]

Master Document – Do Not Disclose                                                    2
   Voltage cut-in : From graph V(cut-in)=0.78V       [0.7V to 0.8V]
   Forward resistance (after cut-in) : R(D1)=dV(D1)/dI(D1)
=(978-878)/(171-75)=1.16 ohm               [1 to 1.4 ohm]

1. For hwr.cir what is the value of the diode voltage when it is in the off state?
[1 mark]

 For 1V sin wave => diode ½ positive wave @ Vmax=430mV
 Diode cut off voltage is @ 300mV         [300mV to 450mV]

1. For bjtochcs.cir what is the mid characteristic value of the output resistance?
[1 mark]

   Operating point : (3.73V,179mA) (5.54V,369mA) => dV=1.81V, dI=90mA
 mid characteristic o/p R : (4.5V,265.9mA) (5.5V,269.4mA) => R=dV/dI=286
[250 to 350 ohm]
1. Comparing inverter.cir and sdbi.cir what is the difference in terms of inverter
performance? [1 mark]

Master Document – Do Not Disclose                                                    3
         INVBJT                            INVBJTSchottky
   INVBJT = slower, INVBJTSchottky = more ideal (can use response time)

1. For bjtdcll.cir what is the effect of varying Re as indicated and how else could the
load line be determined? [2 marks]
 Rc=20 => Vcc=1.500E+01 I(Rc)= 3.038E-02 V(3,4)= 6.468E-02
Rc=120 => Vcc=1.500E+01 I(Rc)= 2.517E-02 V(3,4)= 1.087E-01
Rc=220 => Vcc=1.500E+01 I(Rc)= 1.519E-02 V(3,4)= 4.498E+00
Rc=320 => Vcc=1.500E+01 I(Rc)= 1.057E-02 V(3,4)= 6.634E+00
 As Rc increases, I(Rc) decreases and V(3,4) increases

1. For bjtssafr.cir what are the values for the 3dB frequencies and the mid-band voltage
gain? [2 marks]

   3dB frequencies : [30Hz to 40Hz] (low) and [5.5MegHz to 6.5MegHz](high)
   Mid-band gain = 40dB or Voltage gain =100

1. For ld.cir summarise the behaviour of the circuit’s output. [1 mark]

Master Document – Do Not Disclose                                                         4
   Asymmetric square wave output (V(5)) (duty cycle<50%)
   Threshold for level detector when V(1)sin>V(2)=2V due to OpAmp level
comparator config.
   Output voltage (+12/-12V)

1. For ia.cir what are the values of the 3dB corner frequencies and the mid-band gain?
[1 mark]

          Transcient analysis                      Frequency analysis
   f(3dB)=[9.5kHz to 10kHz] Gain=40dB from frequency
   Gain= 20log(V(4)/V(1))= 20log(2/0.20)=20log(100) from transcient

1. For bpa.cir what are the values of the 3dB corner frequencies and the mid-band
gain? [1 mark]

 Mid-band gain = 0dB
 F(3db,low cut-off)=[15kHz to 17kHz]
 F(3dB, high cut-off)=[1.5MegHz to 1.7MegHz]
1. For ttlnand.cir how does its performance compare with that of the switch-based
NAND and try to briefly identify reasons why this might be. [1 mark]

Master Document – Do Not Disclose                                                        5
   TTL NAND is slower (transcient signal) and with glitches

1. Briefly describe the function of one of each of the types of PSpice statements that
you have encountered. [2 marks]
 .AC (AC anal for magnitude and phase, for V and I)
 .DC (DC anal for voltage @ a given node)
 .END (END of circuit description)
 .ENDS (end of sub-circuit definition)
 .LIB (model circuit library in different file/use of predefined Pspice libraries)
 .MODEL (set of device parameters of element used in circuit)
 .PARAM (define circuit parameters)
 .PRINT (result of analysis in .OUT file)
 .PROBE (run Probe simulator)
 .STEP (for parametric sweep)
 .SUBCKT (begin sub-circuit definition)
 .TRAN (for transcient analysis)
 R, V, C, Q, D are parts not functions

[1 mark] for 6 functions
[2 marks] for 12 functions

Master Document – Do Not Disclose                                                        6

```
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
 views: 22 posted: 9/29/2012 language: Unknown pages: 6
How are you planning on using Docstoc?