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l-ahrelratory2zP.LJ.T. (Programmable Unijunction Tbansistor)

OBIECTT1ZESAfter you complete the laboratory activities you should be able to:1.1 Understand P.U.T. operation and biasing1.2 Measure P.U.T. characteristics and determine P.U.T.

parameters (voltage, current).1-.3 Construct P.U.T. oscillator1.4 Troubleshoot P.U.T. circuits.EQI]IPME\IT1 Master board

1 PU-2000 mainframe

1 EB-113 printed circuit board1 Dual trace oscilloscope

1 Signal generator

1 D.M.M.

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3.0 DISCUSSIONThe P.U.T. (Programmable Unijunction Transistor) is a four layerpnpn device with-three terminals: cathode K, anode A and gate G.

The conduction parameters between the anode (A) and catho^de (K)are controlled by the gate (G). The are two stable states for theconduction betwben A nd K. In state off there is no conduction

. between A and K. In state on there is a very high conduction betweenA and K and low voltage between them. To change state offto on weraise the voltage between A and G until we reach Vp an-{ then wereach state ori Vp is determined by the voltage supplied to G.

T,ABORATORY 2-2

4.O PROCEDI.IRENOTE: If you are just beginning the lab session, set the experimentmarker to 8 by using the procedure given in the GeneralInformation.

Measuring of P.U.T. Characteristics

Increment the experiment marker to "9" by pressing "*" once.

Insert the EB-113 printed circuit board in the PU-2000 cardguides and connector.

3. Locate the circuit that contains P.U.T. (Qr). This circuit is in theupper middle part of the printed circuit.

4. Adjust PS-1 to its minimum voltage.

5. Measure Vs and compare with the formula:

12.RsVs=

Rs+Rs

6. Connect the circuit in Fig.1. by the following procedure.Ajust CH1 probe to x10.

1.

,

(+)PS - 1

7.

8.

Fig. l: Circuit for Measuring p.U.T. parameters

a- connect the jumper between p.u.T. cathode and ground asshown in Fig. 1. -b' Tum the potentiometer RVr fully counterclockwise.c' connect ampermeter to measure anode current,as shown inFig. 1d. connect ch-annel I of the osciloscope to rneasure anodevoltage as shown in Fig. 1observe vA voltage increasing. Adjust ps-1 slowry clockwise.The anode voltaqe vA will increase up to the maximum and thenfall down. Recoid rh" ;;;a;-i,ittugu and rhe current in rhismaximum (peak) point.VP= [V] rP= tuAl

Y^o^L*^lf PS-1 is not enough to find vp, Ip then rurn RVr slowlyclocl

9. Increment the experiment marker to "10" by preSSirlg "*" OnCe.10. Carefully turn potentiometer Rvr clockwise. The voltage V4 w-ill

fall down to id minimum value (the valley point). Record theanode voltage and current at the valley point.

I"ABORATORY 2-4

Vv= [V] Iv= tmAl

VF= [V] IF= tmAlNOTE: In order to find the accurate Vtr', R must be lower toenable more current.

P.U.T. Oscillator

12.InCrement the experiment marker tO "11" by preSSing "'1.'' Once.

13. Connect the circuit in Fig. 2.by the following procedure.

(+)PS -1

11. continue turning potentiometer RVr clockwise. observe that theanode voltage cnges very slowly but changes in current arerapid. Recor the anode voltage and current when potentiometerR is fully clockwise.

Fig. 2: Put - Based Oscillator

Connect the jumpers as shown in Fig. 2.connect channel I of the oscilloscope to observe p.u.T. anodevoltage as shown in Fig. 2. (Use xf pnOnEi -connect channel II of the oscilloscope to observe p.u.T. gatevoltage as shown in Fig.2.

14. Jgrn potentiometer Rvr until oscillations are observed. AjustPS-1 to its maximum value.15. observe the anode and gate vortage and sketch them in Fig. B a, b.

a.

b.

c.

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Fig. 3a: Anode Voltage Waueform

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Fig. 3b: Gate Voltage Waueform

Fig. Bc: Cathode Voltage Waueform

16. Increment the experiment marke r to "L2" by pressirg ,'*,, once.

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IABORATORY 2-6

17. Move the channel II to observe P.U.T. cathode voltage and sketchin Fig. 3c, move the channel back to the gate.

18. Adjust Rvr to get 100H2 oscillations.1g. Move the jumper from c+ capacitor to ca capacitor (ce > c).20. Measure the frequency of the oscillations. Frequerr"r t.

-

tfrlJustify the increse of the capacitor to the decrease in frequency.

option: From measured frequencies and capacitor values.

e3 = 1rFC4 = 0.1l"rF

Find the value of R using frequency equation given in discussionpart. (You may measure R to assure yourselfl.

21. Move jumper from Cs capacitor to C+ capacitor again.Measure amplitude of oscillation V =- fVPtPf

Connect Rz in parallel to Re with a jumper.

Measure amplitude of oscillation V =- fVPtPf

Record frequency of oscillation F =- EIzlWhy did the frequency increase ?.

22. Increment the experiment marker to "13" by pressing "*" once.

23. Rotate the potentiometer Rvr and observe that it caues changesin frequency (and not influence voltage level).

Practice Mode

24. Increment the experiment marker to "14" by pressing "*" once.

25. Adjust Vs to 100H2 by using Ca, observe the waveforms of theanode and gate (V's). For the anode use x10 Probe.

26. To enter the practice mode follow the procedure in Fig. 4