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Current Sources/Mirrors
Published in Amir M. Sodagar, Analysis of Bipolar and CMOS Amplifiers, 2018
Basically, a current mirror is a circuit that receives a current at the input and provides a copy of it at the output. This function can be theoretically modeled by a dependent current source, as mentioned before. Current mirrors are used to copy both DC and AC currents. In the applications where a current mirror is mainly employed to take part in the AC function of a circuit, its input and output resistances become important. Because the input and output signals are currents, an ideal current mirror is expected to have zero input resistance and infinite output resistance. For the real current mirrors in Figure 6.7, we have: () Ri=1/gm1,
Analog Circuit Cells
Published in Wai-Kai Chen, Analog and VLSI Circuits, 2018
Kenneth V. Noren, John Choma, J. Trujillo, David G. Haigh, Bill Redman-White, Rahim Akbari-Dilmaghani, Mohammed Ismail, Shu-Chuan Huang, Chung-Chih Hung, Trond Saether
The current mirror is a circuit that reproduces a reference current at one or more locations in larger circuit. A simple current mirror is depicted in Figure 2.1. Since VBE1 = VBE2, IOUT ≈ IREF, and the reference current IREF is effectively mirrored to another location. In order to evaluate current mirrors and compare the properties of the many types of current mirrors to one another, we first define metrics for current mirrors and characteristics for an ideal current mirror. An ideal current mirror produces and output current that Reproduces a reference current, exactlyDoes not vary with loading (the output resistance [Ro] is infinite)Is insensitive to process variationsIs insensitive to power supply variationsIs insensitive to temperature
C
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
current limiting the output current is limited to a preset level even under a shorted output condition. This can be accomplished by reducing the output voltage to prevent the current limit from being exceeded. current limiting fuse a fuse that limits the level of fault current from that which is available. It operates by developing a substantial voltage across the fuse following the melting of the fuse element. current mirror a configuration of two matched transistors in which the output is a current that is ideally equal to the input current. In the case of a BJT current mirror, the collector of the first transistor is forced to carry the input current. This establishes a corresponding base-emitter voltage, which is applied to the second transistor. If the two devices are matched, then the collector current of the second transistor will equal that of the first transistor, thus "mirroring" the input current. This is a commonly used configuration in integrated circuits, which can take advantage of the inherent matching available by fabricating the two transistors in close proximity to each other. current regulator a device used to control the magnitude and phase of the current in DC, AC
An Inverter Amplifier with Resistive Feedback Current Mirror Gilbert Mixer
Published in International Journal of Electronics, 2023
Devarshi Shukla, Santosh Kumar Gupta, Vijaya Bhadauria, Rajeev Tripathi
The overall Gilbert mixer linearity is controlled by the transconductance stage. It becomes a serious challenge at a lower bias current (Chrisben Gladson et al., 2019; Wan et al., 2011). Ideally, in the differential pair mixer, due to symmetric topology, the even-order harmonics are cancelled out. However, in practical design, even-order harmonics are present at the mixer’s output due to mismatches during fabrication and the LO signal’s duty cycle. A resistive feedback inverter amplifier has been used to exploit the compliment nature of NMOS and PMOS to minimise the second-order harmonic effects. Further, the current mirror offers better linearity and it is independent of bias current (Wan et al., 2012; Bucher et al., 2002). In this analysis, we neglected all parasitic capacitance for simplicity. Assuming small ac voltage signal (vgs) is applied with DC voltage (VGS), the total applied gate-to-source voltage (vGS) is
A novel VLSI design of radix-4 DFT in current mode
Published in International Journal of Electronics, 2019
A. Ganguly, A. Chakraborty, A. Banerjee
The basic circuit element of our proposed design is cascode current mirror. A brief overview of cascode current mirror is provided here. The current mirror circuit provides a replica of a reference current at its output. The current mirror circuit is designed either by using BJT or MOSFET. The advantages of MOSFET over BJT are that it provides higher input and output impedances, lower power consumption and lower area requirement over silicon. Still an ordinary MOS current mirror suffers from the problems of channel length modulation that produces significant mismatch at the output current. This issue is tackled by using cascode current mirror (Razavi, 2001). The effect of channel length modulation is insignificant in cascode current mirror. The circuit of cascode current mirror using n-MOS and p-MOS are shown in Figure 4(a,b), respectively. The output current is the replica of input reference current . If the MOS transistors M1, M2, M3 and M4 are identical, i.e. they have same threshold voltages , same gate to source voltages given by and neglecting the effect of channel length modulation for the cascode current mirror, it can be found that the current entering the transistor M3 equals to the current in transistor M4. Again, considering and .