Ece 203 electrical circuit (7)

YILDIRIM BEYAZIT UNIVERSITY ECE 204 - ELECTRICAL CIRCUITS II 2015 – 2016 Spring Term Project The oscillator circuits take place in radar systems, remote sensing applications such as underground imaging, biomedical applications such as magnetic resonance imaging, telecommunications systems, and might be used in signal & function generators and similar systems. During term project, you are going to deal with specific types of oscillators and components used to realize oscillator circuits. Please, either send your reports in pdf format and deliver hardcopy of your reports up to due date which will be announced. You will need to assemble teams of five students at most. Your effort will absolutely be examined! Note that you could search academic papers at https://scholar.google.com.tr/ ,if required.

1 – Please, draw the schematics of Hartley, Colpitts, Clapp, and Pierce oscillators, and state where negative impedance circuits are used.

2 – Please, derive the current expression of a fully charged capacitor as drawn below with a charge of Q=Qo and potential difference V=Vo in case of short circuiting its two ports suddenly at t=0 under perfectly ideal conditions and state the time – constant & time required to achieve the steady – state response, i.e. when Q achieves 0.

Port - 1

+ Q=Q o, V=V o -

I(t)

Port - 2 Figure – 1: Charged capacitor Hint: Q=CV, i=dQ/dt 3 – Please derive the transfer function of the circuit depicted below, .

Please, state the kind of circuit after deriving the transfer function. Assume that the op amps are ideal, -/+Vcc are sufficiently large and not labeled in figure.

Figure – 2: Two stage op – amp circuit combined with R, L, C components -1-

YILDIRIM BEYAZIT UNIVERSITY 4 – You are required to realize the circuit given in Figure – 2, by opting the op – amp circuits to operate at 5 MHz at most and properly choose the other components to realize the output you are expecting to achieve in case of Vin is a DC source. Also share the gain – frequency graph or gain bandwidth of the op – amp you have opted. Prepare a spice simulation of your circuit by either sharing its schematic and graphs at the output port by using any suitable spice program of your own choice. Please, realize your circuit by a PCB design and provide input & output ports of your circuit by clearly labeling in your PCB. Additionally, please provide a test port to measure the amount of capacitance of C1 , which needs to be a tunable capacitor. The connection of the capacitor should be as depicted below.

Jumper – 1

Jumper – 2

C1

Test Points Figure – 3: Example connection of capacitor for test purpose

Bonus Questions This part must be personal!

1 – Please, make a brief search for PCB & ferrite core based inductors and state at what frequency ranges they are commonly used; a few kHz, MHz or GHz levels?

2 – Please, list the variable capacitor types and briefly explain their tuning mechanisms, mechanical, electrical.

Hint: You could take the basic capacitance formula for a parallel plate capacitor as the reference in your explanation.

3 – Please, list the variable inductor types and briefly explain their tuning mechanisms.

Hint: You could take the basic toroid & solenoid formula as the reference in your explanation.

4 – Please, list the variable resistor types and briefly explain their tuning mechanisms.

5 – Please, draw I – V curve of a BJT transistor provided below and label the saturation and linear regions on the graph. Then derive an equation for time constant of this component by labeling your reference points for your derivation and state the maximum frequency at which this component could operate at.

Ic

Vce Figure – 4: I – V curve of a BJT

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