What is the equation of load current for differential amplifier with an active load?

What is the equation of load current for differential amplifier with an active load?

Signal voltage at the base of Q2 produces a signal collector current i2 = (gmvd) / 2, with direction shown. The two signal currents’ transistors are biased at the same quiescent current, i2 and i4, add to produce a signal current in the load resistance RL.

Why is the current mirror used as active loads?

A current mirror is a circuit designed to copy a current through one active device by controlling the current in another active device of a circuit, keeping the output current constant regardless of loading. The current mirror is used to provide bias currents and active loads to circuits.

What is active load in current mirror?

Most commonly the active load is the output part of a current mirror and is represented in an idealized manner as a current source. Usually, it is only a constant-current resistor that is a part of the whole current source including a constant voltage source as well (the power supply VCC on the figures below).

What is the advantage of active load in differential amplifier?

It turns out that an additional (and perhaps somewhat unexpected) benefit of active loading is that it converts the output signal from differential to single-ended without loss of gain.

Which circuit is used as an active load for CMRR improvement?

current mirror circuit
The important parameter that determines the performance of a differential amplifier is its CMRR which determines the capability of it to amplify the differential mode signal and cancel the common mode signal i.e. noise. To improve the CMRR, the resistor R E is replaced by an active load i.e. the current mirror circuit.

What’s the difference between a mirror amplifier and a fully differential amplifier?

The main difference between single-ended amplifiers and fully-differential versions is that a current mirror load is replaced by two matched current sources in the later. Notice the power dissipation and slew rate is the same.

Can a differential amplifier have active collector loads?

When we discussed a differential amplifier with active collector loads, we noted that such a circuit could not be balanced accurately, and that the circuit would have to be self-balancing to operate effectively. A practical self-balancing circuit is shown to the right.

Can a singled-ended mirror opamp be converted to a fully differential one?

The previous singled-ended current mirror OpAmp can be converted to a fully-differential one as below. Similarly, the complementary design using pMOS at input stage is possible. Which one to use depends on whether the load capacitance or second pole are limiting the bandwidth and whether DC gain or bandwidth is more important.

Which is an active load in differential mode?

The active nature of the load doubles the current delivered to the load with differential-mode inputs, and while not sending any current to the load with common-mode inputs. The results of a more detailed analysis are listed below the figures. Difference-mode inputs: Common-mode inputs: + vic.