An Interesting Filter

Fall 2003ECPE 141 – Advance CircuitsAuthor: Henry Pham

Objectives

Design Specs and Transfer Function

Circuit Simulations & Results Interesting Facts References

Design Specs & Transfer Function 2nd Order Salleen-

Key HPF 2nd Order Salleen-

Key LPF Inverting

Amplifier

Circuit Schematic (Dorf SP16.5)

Realized Circuit

Real Circuit Cleaned Up for Reimplementation

Circuit Simulations & Results

Spice & Lab Output Gain Analysis

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Frequency (Hz)

Gai

n LGain

SGain Measured Gain and Spice Gain

Spice & Lab Output dB Gain

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Frequency (Hz)

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Ga

inLdB Gain

SdB GainMeasured and Spice dB

Gain

ContinueSpice & Lab Output Phase

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Frequency (Hz)

Ph

ase

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rees

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LPhase (Deg)

SPhase (Deg)

Measured and Spice Phase Angle

Continue

Time

0s 20us 40us 60us 80us 100us 120us 140us 160us 180us 200usV(v_vout) V(v_vin)

-15V

-10V

-5V

0V

5V

Transient Response of the Interesting Filter

What happens to the circuit when you replace one capacitor?

Capacitor Change Simulations

Frequency

10Hz 100Hz 1.0KHz 10KHz 100KHz 1.0MHz 10MHzV(v_vin) V(Saleen_Key_High_Pass) V(Saleen_Key_Low_Pass) V(v_vout)

0V

0.5V

1.0V

1.5V

2.0V

V(v_vin) V(Saleen_Key_High_Pass) V(Saleen_Key_Low_Pass) V(v_vout)

Time

0s 20us 40us 60us 80us 100us 120us 140us 160us 180us 200usV(v_vout) V(v_vin)

-15V

-10V

-5V

0V

5V

Frequency Response

Transient Response

Why is it an Interesting Filter?

Lower Stop Frequency at 16Hz 20db/decade

Upper Stop Frequency at 320Hz 20db/decade

Roll-Off at 310kHz 75db/decade

More Interesting Facts Resistors

connecting the entire circuit directly affect gain.

References 1. Al – Hewlett Packard, Design Engineer 2. Joe Carr’s Radio Tech Notes. Filter,

Attenuator, Preamplifier, Preselector - - or Barefoot. http://www.dxing.com/tnotes/tnote07.pdf

3. Dorf & Svoboda. Introduction to Electrical Circuits

Fellow Students and Dr. Khoie