Why do we get error in reference current to output current in basic BJT current mirror?
When the collector-base voltage of a BJT changes, the width of the electric field and corresponding depletion region within the transistor also changes. This is equivalent to a parameter mismatch between transistors, and hence an error in mirrored output current.
What are the advantages of BJT improved current mirror over basic BJT current mirror?
The improved Wilson current mirror circuit is made using 4 transistor versions so it is useful for the operation at high currents. The Wilson current mirror circuit provides low impedance at the input. It doesn’t require additional bias voltage and minimum resources are needed to construct it.
Which parameter affects the current transfer ratio of the BJT current mirror?
Mirror characteristics The first is the transfer ratio (in the case of a current amplifier) or the output current magnitude (in the case of a constant current source CCS). The second is its AC output resistance, which determines how much the output current varies with the voltage applied to the mirror.
Why do we use current mirror?
An important feature of the current mirror is a relatively high output resistance which helps to keep the output current constant regardless of load conditions. Another feature of the current mirror is a relatively low input resistance which helps to keep the input current constant regardless of drive conditions.
What is CMRR formula?
CMRR is an indicator of the ability. 1) and Acom is the common mode gain (the gain with respect to Vn in the figure), CMRR is defined by the following equation. CMRR = Adiff /Acom = Adiff [dB] – Acom [dB] For example, NF differential amplifier 5307 CMRR is 120 dB (min.)
How do I convert CMRR to dB?
Common Mode Rejection Ratio (CMRR) and The Operational Amplifier
- CMMR = Differential mode gain / Common-mode gain.
- CMRR = 20log|Ao/Ac| dB.
- PSRR= 20log|ΔVDc/ΔVio| dB.
- Error (RTI) = Vcm / CMRR = Vin / CMRR.
- Vout = [1 + R2/R1] [ Vin + Vin/ CMRR]
- Error (RTO) = [1+R2/R1] [Vin/CMRR]
- ΔVout = ΔVin / CMRR (1 + R2/R1)
What is slew rate formula?
Slew rate = 2 π f V. Where. slew rate is measured in volts / second, although actual measurements are often given in v/µs. f = the highest signal frequency, Hz. V = the maximum peak voltage of the signal.
Is higher slew rate better?
Higher slew rates are not always better: Higher slew rate makes for higher operating current. This means higher power consumption. Faster slew rate will make higher bandwith.
What is unit of slew rate?
Slew rate is defined as the maximum rate of change of an op amp’s output voltage and is given units of volts per microsecond. Slew rate is measured by applying a large signal step, such as 1V, to the input of the op amp, and measuring the rate of change from 10% to 90% of the output signal’s amplitude.
What is CMRR and slew rate?
Bandwidth is infinity. It means, an ideal op-amp will amplify the signals of any frequency without any attenuation. Common Mode Rejection Ratio (CMRR) is infinity. Slew Rate (SR) is infinity. It means, the ideal op-amp will produce a change in the output instantly in response to an input step voltage.
How is CMRR calculated?
CMRR can be expressed as the ratio between the common-mode voltage (input signal in this case) and the offset voltage generated at the input. The value of the CMRR-induced offset error equals the signal magnitude divided by the CMRR value.
What is the ideal value of CMRR?
100 dB
What is meant by CMRR?
Op Amp Common-Mode Rejection Ratio (CMRR) COMMON-MODE REJECTION RATIO (CMRR) If a signal is applied equally to both inputs of an op amp, so that the differential input voltage is unaffected, the output should not be affected.
Why it is called 741 IC?
IC 741 Op Amp (Operational Amplifier) It was first manufactured by Fairchild semiconductors in the year 1963. The number 741 indicates that this operational amplifier IC has 7 functional pins, 4 pins capable of taking input and 1 output pin.
What is the importance of CMRR?
CMRR is important because it is a measure of the rejection of the common mode signal, the signal that is the same on both the positive and negative input. An instrumentation amplifier amplifies the difference signal, and rejects the common mode signal.
What affects CMRR?
CMRR of the circuit not only depends on Device Under Test (DUT) but also on external component tolerances. Higher is the tolerance, worse is CMRR.
Which one is the method to improve CMRR?
High resistance RE will reduce the common mode gain thus improving the CMRR. i. The circuit in which the output current is forced to equal the input current is said to be a current mirror circuit.
How do I increase CMRR value?
6. To increase the value of CMRR, which circuit is used to replace the emitter resistance Re in differential amplifier? Explanation: Constant current bias offers extremely large resistor under AC condition and thus provide high CMRR value.
How do you increase common mode rejection ratio?
Increasing the Common-Mode Rejection Ratio of Differential Amplifiers Through Precisely Matched Resistor Networks
- For example, a desired gain of G = 1 and the use of resistors with a tolerance of 1% matched to 2% in the amplifier circuit yields a common-mode rejection ratio of.
- or in dB.
Which circuit is used as active load for CMRR improvement?
current mirror circuit
Which circuit is used as active load for an amplifier?
Which factor makes the differentiator circuit unstable?
which factor makes the differentiator circuit unstable? Explanation: The gain of the differentiator circuit (RF / XC1) increases with increase in frequency at a rate of 20dB/decade. This makes the circuit unstable.
Why capacitor is used in differentiator?
The capacitor only allows AC type input voltage changes to pass through and whose frequency is dependant on the rate of change of the input signal. At higher frequencies the reactance of the capacitor is much lower resulting in a higher gain and higher output voltage from the differentiator amplifier.
Is differentiator a high pass filter?
The differentiator circuit is essentially a high-pass filter. It can generate a square wave from a triangle wave input and produce alternating-direction voltage spikes when a square wave is applied.
Which factor is responsible for causing slew rate?
Which factor is responsible for causing slew rate? Explanation: Capacitors require a finite amount of time to charge and discharge. Thus, a capacitor inside or outside the op-amp causes slew rate.
What is IC 723?
The IC 723 is a general purpose, extremely versatile voltage regulator IC, which can be used for making various types of regulated power supplies such as: Positive Voltage Regulator. Negative Voltage Regulator. Switching Regulator.
What is slew rate limiting?
The slew. rate limit is the maximum rate of change of the amplifier’s. output voltage and is due to the fact that the compensation. capacitor inside the amplifier only has finite currents1 avail- able for charging and discharging.
What are the most commonly used active filters?
The most common and easily understood active filter is the Active Low Pass Filter. Its principle of operation and frequency response is exactly the same as those for the previously seen passive filter, the only difference this time is that it uses an op-amp for amplification and gain control.