Basic Elec. Engr Basic Elec. Engr. Lab . Lab ECS 204 ECS 204 Asst. Prof. Dr. Prapun Suksompong prapun@siit.tu.ac.th Operational amplifier • Lab 8 V2I and I2V Converters • Inverting Integrator • 1
V2I and I2V Converters in out in out L L V2I Converter I2V Converter 2
V2I and I2V Converters F in out in R out L out in F R R R V V V 1 V F F out in out in R R R R Non-inverting Amplifier Inverting Amplifier 3
V2I and I2V Converters in out in out L L V out = -I in R I out = V in /R These relations hold regardless of the value of R L . 4
A: Voltage-to-current converter I out = V in /R V in , V I out , mA 1 3 6 10 5
B: Current-to-voltage converter V out = -I in R Current Source I in , mA V out , V 1 3 6 10 6
Part C: Inverting Int Integrat grator or i t i t i C v t d i C v t o R dt 1 t 0 v t v v t dt o o i RC 0 T As a Ramp Generator… Area = hT/2 v t h i 2 Zero-average input h h (DC offset = 0) Sawtooth waveform 1 T h v t 2 7 RC o
Inverting Integrator (2) i t i t i C v t d i C v t o R dt 1 t 0 v t v v t dt o o i RC 0 T An input with nonzero mean (DC offset) can saturate the op amp. v t i v t o 8
Inverting Integrator: AC SS Analysis Z C V V o i R 1 V i R j C The gain at f = 0 is unbounded. Act like an active low pass filter , passing low frequency signals while attenuating the high frequencies. 9
(w/ DC Gain Control) Inverting Integrator w/ Shunt Resistor In practical circuit, a large resistor R p is usually shunted across the capacitor R / / Z R C p C V V o i R R V+ R V p i X i 1 + R j R C v p v + - V- Observe that at f = 0, the gain is finite. 10
Inverting Integrator w/ Shunt Resistor R p Output is not triangular. T “Virtually triangular” if R C C p 2 1 1 R V+ R C p 2 2 fC fR X i in p + v i v o + - V- v t h i 1 Rp r v t h o 1 R r 1 exp r R C 2 11 fR C p p
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