Current mirror

EXEHC15E 143 The circuit below is a current mirror and is a constant current source of about 50 pA. Display how the collector current of Q2 varies with temperature. Let resistors have a linear temperature coefficient of 200 ppm. The part name of both transistors is LM3046-Q. 

The current mirror appears to be relatively independent of temperature. 

The Widlar current source appears to be very temperature dependent, much more than the current mirror. 

Current mirror distributes the photodiode output current to the solar sensor output and the twilight sensor output. 

In 2001 Sony demonstrated a different four TET current-programmed approach using a current mirror, shown in Eigure 6.4.23 [52]. This pixel operates similarly to... 

FIGURE 6.4.23 Sony four TFT self-compensating current-programmed AMOLED pixel using a current mirror. 

An alternative approach is the use of a current drive, in which a programming current is latched in the cell. One approach is to build a current mirror in which one arm is driven through a dummy load and then latched to the other arm (containing the OLED) each cycle. This linearizes the drive in current and also compensates for some spatial variation across the panel. Yet another approach is to drive the latching element itself and sustain the driven current. While complicated from a circuit perspective, this approach has the greatest potential for degradation compensation. Several architectures and their modeling are explored in [135]. 

A coupled array consisting of two or more parallel 1D arrays, which are isolated from each other, could work as a quantum current mirror or even as a quantum current transformer. Because each cluster of the array is capacitively coupled to a corresponding cluster in the parallel chain, a current flow in one array could induce an equally large current of the opposite sign in the other array. 

Careful design of the front end (Table 2) can considerably increase the performance. The advantage is most prOTiounced for miniaturized electrodes with low sensitivity. Since the electrode impedance depends considerably on current density, it is advisable to hold the current density constant or the same in the MUT and reference branch, as it is accomplished in Table 2 A (current excitation). A symmetric Howland-type current source supplies both the MUT and the reference with a current of the same amplitude but opposite polarity. Although, a single current source with current mirror can be used as well. Availability of integrated circuits like ADS 129/8130 (Analog Devices) makes the approaches, as shown in Table 2, favorable. 

This book claims to discuss this topic as broadly as possible and also critically in order to present the reader with as complete a picture as possible. Despite all the technological challenges, it is important to emphasize that a CMS can be implemented as a replacement for mirrors and that the discussed advantages can outweigh the disadvantages. First studies have also shown that drivers can drive with CMS with comparable safety to current mirrors (see the study in chapter Camera-Monitor Systems as a Replacement for Exterior Mirrors in Cars and Trucks ). 

Consequently, the currently used mirror systems entail that the surroundings have to be monitored through foveal vision (also demonstrated in [19] [20]). This, in turn, means that drivers using the current mirror systems must deliberately direct their sight to the respective rnirror in order to see the areas to the side and back of the vehicle. This is not an issue for the primary rear view mirror in the buck because it is directed into the distance (to the rear) and thus corresponds perfectly to the evolutionary purpose of foveal vision, namely the targeted localization and perception ( spotting ) of distant objects (near the far point). 

In the conventional 1 1 replacement, the trailer obscures the viewing area (as is also the case in the current mirror system). The driver is forced to shift their attention to the wide-angle image area. The cyclist can only be detected after this action is performed. 

The current mirror systems do not only impede the flow around the vehicle but also block the direct view from the vehicle (Fig. 5 [27, p. 41], [71, p. 10]). For the homologation of commercial vehicles in Germany the Guideline for the vision of motor vehicles [82, Sect. 35b] has to be fulfilled. This regulation describes the... 

Over the past decades, mirror systems have been adjusted due to changed and expanded regulations [83, Annex 6], [84, par. 1.5.2.4] and ergonomic developments by the system suppliers and car manufacturers to meet the requirements of changing transportation task (see Sect. 1.1.1). The current mirror systems thus are the reference for the development of new electronic vision systems, such as the CMS (see [90] Scope). 

OTA has critical effects on the overall performance of the amplifier such as input equivalent noise, offset voltages, and common-mode rejection ratio (CMRR). A current-mirror OTA with cascade output stage [13] is commonly used in conventional designs. 

Yoon et al. (1999) Design and Implementation of Infrared Readout Circuit Using aNew Input Circuit of Current Mirroring Direct Injection (CMDI) by N. Yoon, B. Kim, H. Lee, and C. Kim, Opto-Electronic Review 7(4), 321-326. 

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