Abstract 2000

A new current mirror structure is introduced , The structure uses non rectangular double drain devices with shared channels to reduce the matching sensitivity to linear parameter gradients . Compare the new structure with the traditional common centroid layout , To obtain the threshold voltage gradient across all angles of the mirror active region . It turns out that , In some applications , Compared with the matching features that can be achieved using traditional layout technology , The proposed non rectangular structure can achieve significant improvements .

background

In parallel with the growing demand for cost-effective high-end mixed signal systems is the demand for improved matching performance in basic circuit blocks . Researchers have proposed models for predicting the matching characteristics of tightly placed devices [1-3 1, But these models are almost entirely used to evaluate the performance characteristics of circuits and layout technologies , This has a history of more than 20 years .
It is generally accepted that , The matching performance of closely placed equipment is affected by the systematic and random changes of equipment characteristics . The traditional method for managing the impact of random changes is to increase the area of matching key equipment to a level that reduces the impact of random mismatch to an acceptable level . It is generally assumed that the system effect is represented by a linear gradient in the matching sensitive part of the circuit , And common centroid placement techniques are usually used to minimize the influence of linear gradients . The standard generic centroid placement technique for current mirrors or differential pairs uses two cross connected rectangular transistor pairs .Felt wait forsomeone .[3] Recent reports , Even with good layout technology , The influence of system change is usually equivalent to that of random change , Therefore, it affirms the need to manage both the system and the impact of random changes .
Integral model , Discussed in the next section , It is widely used to model the effect of parameter gradients through the effective area of transistors . It can be easily shown with the integral model , The effect of linear parameter gradients occurring at any angle is eliminated with any common centroid placement technique , Observe the obvious contradiction in [4]. Some new current mirror layout techniques are introduced [4] Provide the effect of reducing linear parameter gradient and traditional implementation. What is the common layout structure of the center of gravity .

In this paper , The influence of parameter gradient on a kind of current mirror with non rectangular structure is studied , The active channel region of the mirror is shared between the input and output of the device . With the existing mirror circuit ( The matching sensitive part of the circuit is composed of two source coupling transistors ) contrary , The non rectangular structure discussed in this paper is a 4 End device , It can be regarded as a double drain transistor . Although the threshold voltage (V,), mobility (U),COX Even changes in some other parameters will affect image matching , But the main effect is usually the change of threshold voltage . In this paper , Only the influence of spatially related threshold voltage changes is considered . Specially , It shows that the proposed non rectangular mirror structure can be designed , So that the sensitivity of the mirror gain to the gradient in the threshold voltage is significantly lower than that achieved by the widely used common centroid structure .

research

Data sets

Experimental index

The specific methods

Worth following up

Mao-Feng Lan and R. Geiger, “Gradient sensitivity reduction in current mirrors with non-rectangular layout structures,” 2000 IEEE International Symposium on Circuits and Systems (ISCAS), 2000, pp. 687-690 vol.1, doi: 10.1109/ISCAS.2000.857188.