Medical instrumentation

The small signal transconductance of a transistor (gm) is defined as: The voltage gain of the associated amplifier. The slope of the Id= f(Vgs) characteristic of the transistor in saturation obtained as the Bias Point. It is always the slope of the Id= f(Vgs) characteristic of the transistor obtained as the Bias Point. The DC current gain of the transistor.

Ideally, the input current of a MOSFET transistor is: Zero. Infinity. The input voltage divided by the input impedance in saturation and for the Bias Point. None of the above.

The small signal model of a MOSFET include two internal capacitors responsible for the high-frequency response of the device. Those capacitors are known as: a) Cgs and Cgd. b) Cgs and Csd. c) Csd and Cgs. d) Depending on the configuration, it can be either a) or b).

A voltage amplifier has a Gain-Bandwidth product of 16 MHz and an open loop gain of 100dB. What will be the high cut-off frequency of a voltage follower made using such amplifier?. 160 Hz. 16 KHz. 160 KHz. 16 MHz.

In a real differential amplifier, the CMRR (Common Mode Rejection Ratio): Is the ratio between the DC leve! of the input signal and the AC gain of the amplifier. Is the ratio between the differential and common mode gains. Depends on the input impedance. Has a valueof 100 dB.

In an inverting amplifier, What is the phase shift between the input and output signáis at the high cut-off frequency?. 0º. -135º. -180º. -225º.

In a non-inverting amplifier using a real O.A.: The input offset voltage induces a non-linear response of the amplifier. The input offset voltage reduces the available gain for the input AC signal. The input offset voltage and the desired signal are both amplified, and with the same gain. None of the above.

The SIew Rate (SR) of a given Operational Amplifier is 50 V/microsecs and its Gain-Bandwidth Product is 10 MHz. The SR will always limit the máximum operation frequency for sinusoidal signáis if the Gain is bigger than 10. The high cut-off frequency will be always limited by the Gain-Bandwidth Product. If the Bias Voltage of the OA is bigger than 10 V, the S R will set the máximum operation frequency for sinusoidal signáis if the Gain is one (follower). None of the Above.

In a second order Band-Pass (BP) filter built by cascading a low-pass (LP) and a high-pass (HP) Sallen-Key filter: The roll-off of the frequency response after the central frequency of the filter is -20dB/dec. The Q factor depends on the cut-off frequency of the HP filter (among other parameters). The roll-off of the frequency response before the central frequency of the filter is -20dB/dec. Both b and c are true.

In an oscillator built using the Wien Bridge configuration: The bandwidth of the operational amplifier that forms part of the oscillator must be equal or greater than the oscillation frequency. The Slew-Rate of the operational amplifier that forms part of the oscillator does not affect the output signal of the oscillator. The closed loop gain of the operational amplifier that forms part of the oscillator sets the maintenance condition. The output voltage of the oscillator depends on the oscillation frequency.

In an inverter amplifier, the operational amplifier has a finite Slew-Rate. If the output voltage is: Vout=1·sin(2pi·10k·t) V. The minimum Slew-Rate of the operational amplifier must be 10V/ms. The maximum Slew-Rate of the operational amplifier must be 10V/ms. The Slew-Rate does not affect the output voltage. The maximum input voltage depends on the Slew-Rate.

A class D power amplifier with VDD= 10V is used to drive a load of 5 ohms. Each MOSFET in the complementary stage has a voltage of VDSon=0.6V, then: The power dissipated in the load is equal to aprox. 17.7W. The efficiency of the power amplifier is 95%. Both a and b are true. The efficiency of the power amplifier is 50%.

In an instrumentation system, an antialiasing filter is used to. Amplify the voltage of the input sensor. Smooth the output pulses of a Digital to Analog converter. To remove parts of the signal we don’t want in the sampling process. Eliminate the low frequency signals.

The high cut-off frequency of an amplifier is typically limited by the: Transistors’ parasitic capacitances. Coupling Capacitors. The CMRR of the amplifier. The input and output impedances.

In a real non inverting amplifier, the CMRR: Is the ratio between the DC level of the input signal and the AC gain of the amplifier. Is the ratio between the differential and common mode gains. Depends on the input impedance. Has a value of 100dB.

The roll-off of a three-pole low -pass filter is: – 40dB/dec. - 60dB/dec. +40 dB/dec. +20 dB/dec.

What limits the maximum oscillation frequency of a linear oscillator (for example, a Wien Bridge oscillator): The GainxBandwidth product of the Operational Amplifier. The Coupling Capacitors. The actual gain of the amplifier. None of the above, the oscillation frequency is always fixed by the external capacitors and resistors.

A 10 channel Data Acquisition Board incorporates a single 100 MS/s Digitizer. Which of the following sentences are TRUE? (Mark all of those that apply). The maximum sampling speed if we are using the all ten channels is 10 MS/s. All the channels are acquired at the same time instants regardless of the sampling frequency. The antialiasing filter at the inputs should be of 50 MHz. No antialiasing filters are needed in any case.

Which is the center frequency of a band-pass filter with low cut-off frequency of 1 MHz and a high cut-off frequency of 100 MHz?. 50 MHz. 50.5 MHz. 25 MHz. 10 MHz.

Mark all the sentences that are TRUE regarding electronic filters: Active filters may present a gain bigger than one in the pass band. Passive filters have always smaller roll-offs than active filters. The number of poles and the roll off of active filters depend on the number of capacitors in the circuit. The number of poles and the roll off of passive filters depend on the number of capacitors and the resistors in the circuit.

In an oscillator built using the Wien Bridge configuration: The bandwidth of the operational amplifier that forms part of the oscillator must be equal or lower than the oscillation frequency. The Slew-Rate of the operational amplifier that forms part of the oscillator does not affect the output signal of the oscillator. The closed loop gain of the operational amplifier that forms part of the oscillator sets the maintenance condition. The oscillation frequency depends on the input voltage of the oscillator.

A class D power amplifier is used to: amplify voltage. drive sensors. connect a microcontroller and an actuator. filter the DAC signal.

A class D power amplifier with VDD=10V is used to drive a load of 5. Each MOSFET in the complementary stage has a voltage of VDSon=0.1V, then: a) The power dissipated in the load is equal to ~ 20W. b) The efficiency of the power amplifier is 98%. c) Both a and b are true. d) The efficiency of the class D amplifier is lower than a class A amplifier.

If we want to acquire a signal of 18 MHz bandwidth (maximum frequency component), What is the minimum sampling frequency required?. 18 MHz. 36 MHz. 9 MHz. None of the above.

The phase condition in a linear oscillator (for example, a Wien Bridge oscillator) fixes: The oscillation frequency. The amplitude of the output signal. Both the amplitude and the oscillation frequency. Neither the amplitude nor the oscillation frequency: it is required to start the oscillation.

Which is the centre frequency of a band-pass filter with a quality factor (Q) of 10 and a bandwidth of 1 MHz?. 100 kHz. 1 MHz. 10 MHz. 100 MHz.

If we talk about power amplifiers: Class A amplifiers are more efficient that Class D amplifiers. The efficiency of a power amplifier depends on the amplitude of the output signal. The efficiency of a power amplifier does not depend on the amplitude of the signal. Class D amplifiers can be built with just one transistor.

What is the roll-off for a low -pass filter that includes two capacitors?. - 40dB/dec. - 60dB/dec. +20 dB/dec. +40 dB/dec.

If we use a sine wave signal Vosc with a peak voltage of 2.5V to drive a comparator like in the figure, how is the output signal Vout?. A sine wave of 2.5V peak. A square signal of VCC/2 peak. A sine wave of VCC peak. A square signal of 2·VCC of amplitude (peak to peak).

The input signal to an ADC is -6dBV compare to its Full-Scale voltage, if the number of bits of the ADC is 12bits, what is the Signal-to-Noise Ratio (SNR) of the ADC?. 74dB. 80dB. 68dB. We need to know the full-scale voltage to calculate the SNR.

A Sample and Hold (S&H) circuit has a capacitor of 12pF. The input signal has 1Vpeak, what is the SNR at the output of the S&H due to thermal noise? Note: k·T=4.14·10(^-21). 9dB. 91.6dB. 14.9bits. We need to know the equivalent resistor of the S&H circuit to calculate the SNR.

A DAC with a reference voltage of VREF = -4V, like in the figure, is used to drive an actuator. If S2 is opened, S1 is opened and S0 is closed, what is the output voltage, Vout, of the DAC?. -16V. -1V. 1V. 4V.

A DAC with a reference voltage of VREF = -4V, like in the figure, is used to drive an actuator. If S2 is opened, S1 is opened and S0 is closed, what is the LSB voltage of the DAC?. 1 V. 2 V. 0.5 V. 4 V.

We have an inverting amplifier whose output is a sinewave of 1Vpeak when the input is a sinewave of 1mVpeak. The amplifier has a gain of 100 dB. The amplifier has a gain of 30dB. The amplifier has a gain of 60dB. The amplifier has a gain of -60dB.

The parasitic capacitances of transistors are typically responsible for. The low cut off of an amplifier. The mid gain of an amplifier. The high cut-off of an amplifier. The CMRR of an amplifier.

A voltage amplifier has a feedback circuit that reduces its open loop gain from 1000 to 10. Its input impedance when the feedback loop is open is 1KOhm. In closed loop the input impedance will be. 10 Ohm. Zero. 100 KOhm. 1 KOhm.

A voltage amplifier has a Gain Bandwidth product of 1MHz and an open loop (no feedback) gain of 40dB. The high cut off frequency of the open loop amplifier is. 1MHz. 25KHz. 100Hz. 10KHz.

In a real non inverting amplifier, the CMRR: Is the ratio between the DC level of the input signal and the AC gain of the amplifier. Depends on the frequency of the input signal. Depends on the input resistor. Has a value of 100dB.

In a real inverting amplifier, the Slew-Rate of the O.A.: (mark correct one(s)). Sets the maximum output voltage that can be reached. Depends on the amplifier gain. Sets the maximum slope of the output voltage signal. Depends on the input signal frequency components.

In a Bio-Potential signal acquisition system: The Instrumentation Amplifier is used to attenuate the signal from the sensor. The Instrumentation Amplifier is used to reject the offset level of the sensor. The Instrumentation Amplifier is used to accommodate the AC signal of the sensor. The Instrumentation Amplifier is used to filter the signal of the sensor.

The instrumentation amplifier AD620: Has always a Bandwidth below 120kHz. Has a CMRR that depends on the gain of the amplifier. Is normally used with low voltage gain. Has a large input offset (>1mV).

An amplifier with a gain of 20dB has. A power gain of 10 in absolute value. A voltage gain of 10 in absolute value. The same gain in power and in voltage when expressed in absolute values. None of the above.

The small signal equivalent of a MOS transistor at mid frequencies: Is a voltage controlled current source. Is a voltage controlled voltage source. Is a voltage controlled current source with a capacitor in parallel with the gate and the source. Is a voltage controlled resistor.

In an oscillator built using the Wien Bridge configuration: The oscillation frequency depends on the input voltage of the oscillator. The closed loop gain of the operational amplifier that forms part of the oscillator sets the maintenance condition. The Slew-Rate of the operational amplifier that forms part of the oscillator does not affect the output signal of the oscillator. The bandwidth of the operational amplifier that forms part of the oscillator must be equal or lower than the oscillation frequency.

A Wheatstone bridge is used in biomedical instrumentation systems: to transform an electrical magnitude into a physical magnitude. as part of the sensor interface of the system. to keep the linearity of the sensor. to increase the input impedance of the instrumentation system.

In an Instrumentation Amplifier, which of the following parameters depend on the signal frequency?. voltage offset. common mode rejection ratio. bias current offset. the DC gain.

The quality factor Q of a band pass filter depends on: The bandwidth of the OpAmp used in the filter. The central frequency of the filter. The slew rate of the OpAmp used in the filter. The roll-off of the filter.

Why an antialiasing filter is needed when using A/D converters in an instrumentation system?. To remove the DC component of the sensor. To extend the bandwidth of the A/D converter. To remove unwanted frequencies from the sensor. To adapt the sensor signal to the full-scale of the A/D converter.

In an A/D converter, the quantification step depends on: The Signal-to-Noise Ratio of the converter. The power consumption of the converter. The architecture of the converter. The frequency of the input signal to the converter.

What is the Signal-to-Noise Ratio of an A/D converter that has an input signal power of 0.5 V2/Hz and an error power of 5·10^(-9) V^2/Hz: 8dB. 80dB. 320dB. 160dB.

An instrumentation system with a gain of 20dB has. None of the above. A power gain of 10 in absolute value. The same gain in power and in voltage when expressed in absolute values. A voltage gain of 10 in absolute value.

In the microcontroller used in the lab sessions (Arduino One): The digital pins are bidirectional. The analog pins are bidirectional. The power pins are input only. None of the above.

The roll-off of a two-pole high-pass filter is: -40 dB/dec. -60 dB/dec. +40 dB/dec. +20 dB/dec.

A 8 channel Data Acquisition Board incorporates a single 50 MS/s Digitizer. The maximum sampling speed if we are using the all eight channels is 50 MS/s per channel. The antialiasing filter at the inputs should be of 50 MHz. If we want to acquire a 25 MHz bandwidth signal, only one channel can be used. All the channels are acquired at the same time instants regardless of the sampling frequency.

In an oscillator built using the Wien Bridge configuration: The bandwidth of the operational amplifier that forms part of the oscillator must be equal or lower than the oscillation frequency. The Slew-Rate of the operational amplifier that forms part of the oscillator does not affect the output signal of the oscillator. The oscillation frequency depends on the input voltage of the oscillator. The closed loop gain of the operational amplifier that forms part of the oscillator sets the maintenance condition.

A voltage amplifier has an open loop gain of 60 dB and open loop input impedance of 10MΩ. What would be the input impedance when the amplifier is connected in a feedback configuration for a gain of 20 dB?. 1 MΩ. Zero. 1 kΩ. 1 GΩ.

A voltage amplifier has a Gain Bandwidth product of 15MHz and an open loop gain of 120dB. The high cut off frequency of the open loop amplifier is: 15 kHz. 150 KHz. 150 Hz. 15 Hz.

To build an inverting amplifier we use on OA with a Slew-Rate of 50 V/ms: None of the above. For an input signal of 1 mV, the maximum operation frequency is 50 kHz. The gain of the inverting amplifier cannot be bigger than 50 V/V. The Slew-Rate is so high that the maximum frequency of operation will always be fixed by the GainxBandwith product.