How is the drain current of a mirror determined?
The drain current of a MOSFET ID is a function of both the gate-source voltage and the drain-to-gate voltage of the MOSFET given by ID = f ( VGS, VDG ), a relationship derived from the functionality of the MOSFET device. In the case of transistor M1 of the mirror, ID = IREF.
Is the temperature of the current mirror the same?
To maintain matching, the temperature of the transistors must be nearly the same. In integrated circuits and transistor arrays where both transistors are on the same die, this is easy to achieve. But if the two transistors are widely separated, the precision of the current mirror is compromised.
Can a current mirror be approximated by a Norton impedance?
For small-signal analysis the current mirror can be approximated by its equivalent Norton impedance . In large-signal hand analysis, a current mirror is usually and simply approximated by an ideal current source. However, an ideal current source is unrealistic in several respects:
How does a bipolar mirror convert voltage to current?
The simplest bipolar current mirror (shown in Figure 1) implements this idea. It consists of two cascaded transistor stages acting accordingly as a reversed and direct voltage-to-current converters. The emitter of transistor Q1 is connected to ground. Its collector-base voltage is zero as shown.
Can a mirror circuit be implemented using two MOSFET transistors?
Current mirror circuit can be easily implemented using two MOSFET transistors. The working of the MOSFET current mirror circuit is similar as described in the previous transistor section. Consider the above current mirror circuit using MOSFET, the MOSFET transistor M1 is in the saturation region as the V DS ≤ V GS.
How is the drain current reflected in the MOSFET M1?
MOSFET device function like this, the drain current reflects the function of the gate to source and drain to gate voltage. Due to this, the input current in the MOSFET M1, is mirrored to the drain current. In the image, the input current is provided by the bias resistor.
Which is the ideal configuration for a mirror circuit?
A current mirror circuit, mirror or copy the input current of one active device to the other active devices output. An ideal current mirror circuit is an ideal current amplifier with the inverting configuration that can reverse the current direction. Therefore, for an ideal current amplifier, the current transfer ratio is an important parameter.