Amplifiers – With amplifier condition indicating or testing means
Reexamination Certificate
2002-01-24
2004-04-27
Mottola, Steven J. (Department: 2817)
Amplifiers
With amplifier condition indicating or testing means
C330S261000
Reexamination Certificate
active
06727747
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for reusing a resource for designing an operational amplifier, and to an operational amplifier, a layout generating apparatus and a layout generating program which can realize the method of reuse.
2. Description of the Background Art
When designing an operational amplifier, a designer determines various circuit constants such as the bias voltage, the size of each transistor (the gate width and the gate length) etc., to satisfy required characteristics such as the maximum operating frequency, slew rate, etc., and designs the layout pattern including circuit elements and interconnections which constitute the operational amplifier. In order to efficiently design the operational amplifier, existing design resources are reused when the specifications are changed.
In conventional reuse of design resources for operational amplifiers, the designer conducts a simulation and determines circuit constants such as the shrink factor (reducing scale), bias voltage, etc. so that the required characteristics are satisfied, and varies the layout pattern design of the operational amplifier.
In the conventional operational amplifier design resource reuse method, however, the circuit constants have so wide a choice that determining the circuit constants is a time-consuming work. Changing the layout pattern design is also time-consuming since the designer cannot achieve it by selecting an appropriate layout pattern out of a plurality of prepared layout patterns.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for reusing a resource for designing an operational amplifier which can easily reuse an existing design resource and which can shorten the time required for the reuse, and an operational amplifier, a layout generating apparatus, and a layout generating program which can realize the method of reuse.
According to an aspect of the present invention, a method for reusing a resource for designing an operational amplifier comprises the steps of: preparing different sets of layout information for an operational amplifier comprising a plurality of transistors, the plurality of transistors having their channel widths varied by different factors among the different sets of operational amplifier layout information; and selecting one of the different sets of operational amplifier layout information and determining the value of a bias current of the operational amplifier so that a required characteristic is satisfied.
The method of reuse of the invention thus prepares different sets of operational amplifier layout information, where the channel widths of the plurality of transistors are varied in a uniform manner. Then one of the different sets of operational amplifier layout information is selected and the value of the bias current of the operational amplifier is determined, so as to design an operational amplifier which satisfies a required characteristic. An existing design resource can thus be easily reused and the time required for the reuse can be shortened.
The operational amplifier may have a circuit configuration in which a bias voltage generated by a bias generating circuit is applied to a transistor serving as a current source of the operational amplifier, thereby supplying a current corresponding to a constant multiple of a bias current of the bias generating circuit as a bias current of the operational amplifier, and the method of reuse may further comprise a step of previously setting a relation between the value of the bias current of the operational amplifier represented by the different sets of layout information and the value of the bias current of the bias generating circuit so that a set of operational amplifier layout information can be uniquely selected from the different sets of operational amplifier layout information and the value of the bias current of the bias generating circuit can be uniquely determined on the basis of the value of the bias current of the operational amplifier which satisfies the required characteristic.
In this case, the operational amplifier layout information can be uniquely selected from the different sets of operational amplifier layout information and the value of the bias current of the bias generating circuit can be uniquely determined. This remarkably reduces the work load and the time required for optimization to obtain the operational amplifier layout information which satisfies the required characteristic.
The operational amplifier design resource reuse method may further comprise a step of previously setting the different factors and the value of the bias current of the bias generating circuit so that the bias current of the operational amplifier continuously varies.
In this case, since the bias current of the operational amplifier can be continuously varied by varying the bias voltage of the bias generating circuit at each factor, one of the different sets of operational amplifier layout information and the value of the bias current of the operational amplifier can be easily selected and determined to satisfy the required characteristic.
The operational amplifier design resource reuse method may further comprise the steps of determining an upper limit of a bias voltage applied to a transistor serving as a current source of the operational amplifier on the basis of an output voltage range, and determining a lower limit of the bias voltage on the basis of cutoff of the transistor serving as a current source. This enables an optimum bias voltage to be selected.
It is preferred that the different factors include three or four kinds of factors. This remarkably reduces the design time for preparing the different sets of operational amplifier layout information corresponding to the different factors.
The plurality of transistors may further comprise a pair of transistors having a differential configuration and the transistor serving as a current source may supply a current to the pair of transistors. Also, each of the plurality of transistors may comprise a field-effect transistor.
According to another aspect of the invention, an operational amplifier comprises: a plurality of transistors including a transistor serving as a current source; a bias generating circuit that applies a bias voltage to the transistor serving as a current source; and a channel width varying circuit that varies channel widths of the plurality of transistors, thereby realizing a method for reusing a resource for designing an operational amplifier comprising preparing different sets of layout information for an operational amplifier comprising a plurality of transistors, the plurality of transistors having their channel widths varied by different factors among the different sets of operational amplifier layout information, and selecting one of the different sets of operational amplifier layout information and determining the value of a bias current of the operational amplifier so that a required characteristic is satisfied.
In the operational amplifier of the invention, the channel widths of the plurality of transistors can be varied by the channel width varying circuit, so that the operational amplifier design resource reuse method can be realized easily.
The operational amplifier may further comprise a bias voltage adjusting circuit that adjusts the bias voltage generated by the bias generating circuit.
In this case, the bias voltage can be adjusted by the bias voltage adjusting circuit, while the channel widths of the plurality of transistors can be varied by the channel width varying circuit. Then the operational amplifier design resource reuse method can be realized more easily.
The plurality of transistors may further include a pair of transistors having a differential configuration and the transistor serving as a current source may supply a current to the pair of transistors. Also, each of the plurality of transistors may comprise a field-effect transistor.
According to a further aspect of the invention, an operational amplifier comprises: a plu
Tani Kuniyuki
Wada Atsushi
Armstrong Kratz Quintos Hanson & Brooks, LLP
Mottola Steven J.
Sanyo Electric Co,. Ltd.
LandOfFree
Method for reusing resource for designing operational... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for reusing resource for designing operational..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for reusing resource for designing operational... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3235215