1.1. Figure 2. In the previous article, we discussed about Current Mirror Circuit and how it can be built using Transistor and MOSFET.

Single transistor active current … The simple MOS current mirror The simple current mirror can be obtained from the one transistor current source by using a second transistor in diode connection that generates the necessary gate-source voltage of the transistor in the output stage.
In reality, a voltage divider or collector to base resistor is generally used to provide the necessary bias for simple single transistor circuits. Simple current mirror Two implementations exist for the simple current mirror: BJT and MOSFET. For all examples, a transistor with a current gain of 100 is used and the bias current will be set at exactly 100th of the expected collector current (using a simulated current source, naturally). The current source operates because of the fact that the collector current in a transistor circuit is Β times the base current. The NPN current mirror, in its most basic form, is, in effect, an inverting current buffer in the sense that it changes current sources of any impedance into current sinks of high impedance. The three T2 collectors may be joined to give 3I IN. Despite the fact that basic current mirror circuit can be constructed using two simple active components, BJTs and MOSFETs or using an amplifier circuit, the output is not perfect, as well as it has certain limitations and dependencies on the external things. Indeed, a single transistor can act as an amplifying current mirror where the base current is the input current and the collector current is the output current. If the effect of Early voltage is important, it can be minimized by using the slightly more complex Wilson current mirror. OPERATION OF CURRENT MIRROR 1. (a) Multistage current mirror, and (b) noninteger-ratio current mirror.
Both three-transistor and four-transistor versions are shown in Figure 3. BJT The BJT implementation of the simple current mirror is used as a block in the operational amplifier. Although there is a specific relationship between Iref and Vbe, the same Vbe is applied to the Transistor Q2, hence it develops the current similar the collector current of Q1. This is independent of the collector voltage, provided that there is sufficient voltage to drive the current through the load device in the collector. 2. So the name CURRENT MIRROR. Q1 acts like a diode and a current is established through it. MOS current mirrors 1.1.1.