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An ideal current source generates a current that is independent of the voltage changes across it. An ideal current source is a mathematical model, which real devices can approach very closely. If the current through an ideal current source can be specified independently of any other variable in a circuit, it is called an independent current source.
There are three main specifications that characterize a current mirror. 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 ...
This is the only first order source of mismatch in the three-transistor Wilson current mirror [8] Second, at high currents the current gain, β, of transistors decreases and the relation of collector current to base-emitter voltage deviates from = (). The severity of these effects depends on the collector voltage.
The resistance between the drain to source terminals of the JFET increases as the gate-to-source voltage becomes more negative and decreases as the gate-to-source voltage approaches 0 volts. The simulation below bears this out. The output voltage is about 2.5 volts with a gate-to-source voltage of −1 volt.
A Widlar current source is a modification of the basic two-transistor current mirror that incorporates an emitter degeneration resistor for only the output transistor, enabling the current source to generate low currents using only moderate resistor values.
A depletion-mode device with gate tied to the opposite supply rail is a much better load than an enhancement-mode device, acting somewhere between a resistor and a current source. The first depletion-load NMOS circuits were pioneered and made by the DRAM manufacturer Mostek , which made depletion-mode transistors available for the design of the ...
In textbooks, channel length modulation in active mode usually is described using the Shichman–Hodges model, accurate only for old technology: [2] where = drain current, ′ = technology parameter sometimes called the transconductance coefficient, W, L = MOSFET width and length, = gate-to-source voltage, =threshold voltage, = drain-to-source voltage, =, and λ = channel-length modulation ...
Overdrive voltage, usually abbreviated as V OV, is typically referred to in the context of MOSFET transistors.The overdrive voltage is defined as the voltage between transistor gate and source (V GS) in excess of the threshold voltage (V TH) where V TH is defined as the minimum voltage required between gate and source to turn the transistor on (allow it to conduct electricity).