Ronel Vincent P. Vistal 2006 – 40294 EEE 54 – Design Problem 2 I. Problem Specifications Specifications
Devise a Bootstrap ramp generator which output is used as input to a Schmitt trigger that has output fed back to the ramp generator. The output of the Ramp generator has a minimum voltage of
-10V up to maximum voltage of -5V. Also, the circuit output should have a variable frequency ranging from 200 Hz to 3 KHz. The range of frequencies should be covered by the range of majority of the potentiometer. II. Design
D1N4148 D2
50k R4
C1 666p IC=15 IC=15 X2
D1N4148 D3
X2-out C2 20n IC=0
1K R3
LF353
Q1 Q2N2906
100k R5
15 V1
200k R1
X1
D1
X1-out D1N4148 X1-inn D1N4148 D4
LF353 150k R6
470k R7
-15 V2
100k R2
III. Computations
First, compute for R1, R2, R6 and R7. R1 and R2 would be the voltage divider for LTP and R6 and R7 would be the voltage divider for the UTP.
It should also be considered to have R2 and R1 be in 100kΩ range. By choosing from the available components, R1=150kΩ and R2=4700kΩ is chosen. R6 and R7 would also be desired to be in 100kΩ range. By choosing from the available components, R6=200kΩ and R7=100kΩ is chosen For the bootstrap ramp generator, the load resistance would be set to 1kΩ (R3 = 1kΩ). It should also be noted that the maximum reverse current for D1 is 3μA so to allow 1% nonlinearity we would make IR5 = (100)3μA = 300μA
Next, we should make sure that the output could charge up to the max voltage with the maximum frequency.
Next, the range of the potentiometer R5 would be calculated. Since C2 was computed from the maximum frequency we would first compute the minimum resistance for R5. Computing for the maximum resistance for the given minimum frequency: C3 would be computed such that it would only discharge 1% of its original value which is Vcc.
R4 should be large enough to avoid having large base current. A 100kΩ value for R4 was chosen for this design.
Ronel Vincent P. Vistal 2006-40294
EEE 54 – Design Problem 3
I. Design Specifications
Design a Wien Bridge sinusoidal oscillator with oscillating frequency of 48.5 KHz. II. Computations and Design A. RC Phase Shift Network
Since ω = 2π f 0, the new equation to solve for R and C values would be:
Computing the value of A: -9 V2
Assuming that C = 4.7 nF (available cap), solving for the value of R: 2k
The Wien-bridge oscillator has an overall feedback factor of β=1/3, proper sizing of R F and RG is necessary to set A = 3, so that the overall gain of the circuit would be | | . For convenience, RG is set to equal R and R F is double RG.
