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Hi, below schematic is a fully-differential gain-boosting opamp that I'm working on right now. I want to check the stability of a local loop that is comprised of gain-boosting amp and a source follower. So, I inserted 'diffstbprobe red color ' as below, set it as a probe instance, and ran stb simulation for now, I'm using ideal CMFB, so didn't use pstb. However, the dc gain of this loop turned out to be 2.
I've thought that this dc gain should be close to the gain of boosting amp, which is Please let me know if you find any mistake or wrong simulation setup. Furthermore, the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention. Finally, like reference numerals in the figures designate corresponding parts throughout the several drawings.
Having summarized the invention above, reference is now made in detail to the description of the invention as illustrated in the drawings. While the invention will be described in connection with these drawings, there is no intent to limit it to the embodiment or embodiments disclosed therein.
On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. Indeed, the present invention is believed to be applicable to a variety of systems, devices, and technologies.
Turning now to the drawings, wherein like referenced numerals designate corresponding parts throughout the drawings, FIG. Such a circuit includes a positive i. A positive i. The first stage functions to provide gain, that is to amplify the input signal, and also to provide high input resistance and large common mode rejection. The second stage of the op-amp consist of what is commonly referred to in the art as a fully-differential op-amp configuration, which is made up of a plurality of MOSFET's - that are electrically connected, as shown.
The second stage functions to also provide gain and to provide a low output resistance and minimal output signal loss. Electrically interconnecting the first stage and the second stage are coupling resistors , and coupling capacitors , The op-amp is powered from a positive voltage power rail and a negative voltage power rail Additionally, various members - , - , of the plurality of MOSFET's, which make up the two stages , of the op-amp circuit , are biased via bias inputs - Essentially, the conventional op-amp circuit operates to output an amplified version of an input signal that has a frequency within the operating bandwidth of the op-amp The op-amp utilizes Miller compensation to maintain stability, as is known in the art.
Having described a conventional two-stage op-amp circuit, as is known in the prior art, reference now will be made to various embodiments of a fully-differential two-stage op-amp with gain-boosting in the first stage, constructed in accordance with various aspects of the present invention. To this end, reference is first made to FIG.
Where appropriate, reference numerals have been kept the same as those illustrated in connection with FIG. Referring to FIG. The op-amp also comprises a positive output and a negative output which are electrically connected to an output stage In a preferred embodiment, as shown in FIG.
An input or output, as it is referred to in the present invention, may include but is not limited to any thing that may be used as an electrical connector or connection, for example, a terminal, pin, contact, lead, or solder point. The input stage and output stage are electrically coupled, and in a preferred embodiment, as shown in FIG.
Additionally, the op-amp is powered from a positive voltage power rail and a negative voltage power rail The input stage comprises a plurality of MOSFET's - that are electrically connected in what is commonly referred to in the art as a telescopic op-amp configuration. The output stage comprises a plurality of MOSFET's - that are electrically connected in what is commonly referred to in the art as a fully-differential op-amp configuration.
In contrast to the conventional op-amp FIG. Further, and in significant contrast to the conventional op-amp FIG. The gain-boost amplifiers , are electrically connected to the input stage by a plurality of connections - , - , which comprise positive and negative inputs - , - and positive and negative outputs - , - of the gain-boost amplifiers , The gain-boost amplifiers , and the input stage form a local unity-gain feedback.
Therefore, the outputs - , - of the gain-boost amplifiers , are adaptively stabilized. As a result of these characteristics, several notable benefits, among others, are achieved. Second, the op-amp achieves this significant increase in open-loop DC gain without a resultant decrease in its unity-gain frequency, unlike in the conventional op-amp which typically incurs a decrease in unity-gain frequency for an attempted increase in open-loop DC gain.
Third, the op-amp achieves very high open-loop DC gain and maintains very high unity-gain frequency with only a small increase in power consumption, and the circuit requires little additional area in the overall CMOS circuit layout. In a preferred embodiment of the present invention, the gain-boost amplifier is configured to electrically connect to P-channel MOSFET circuitry of the input stage and is therefore referred to as a PMOS gain-boost amplifier.
Furthermore, in a preferred embodiment of the present invention, the other gain-boost amplifier is configured to electrically connect to N-channel MOSFET circuitry of the input stage and is therefore referred to as an NMOS gain-boost amplifier. It is noted that the input stage functions to provide high gain and also to provide high input resistance and large common mode rejection.
Furthermore, the output stage functions to provide additional gain and to provide a low output resistance and minimal output signal loss. Reference is now directed to FIG. The PMOS gain-boost amplifier comprises a plurality of electrically connected MOSFET's - , various members - , , of which are electrically connected to and biased via bias inputs , , The PMOS gain-boost amplifier has what is commonly referred to in the art as a fully-differential op-amp configuration.
In such a configuration, a positive input , a negative input , a positive output , and a negative output are each electrically connected to the PMOS gain-boost amplifier Furthermore, the PMOS gain-boost amplifier is electrically connected to and powered from a positive voltage power rail and a negative voltage power rail Moving now to FIG.
As such, the NMOS gain-boost amplifier includes a plurality of electrically connected MOSFET's - with various members - , , of this plurality electrically connected to and biased via bias inputs , , The NMOS gain-boost amplifier is also configured as a fully-differential op-amp, as such configuration is commonly referred to in the art, and it has a positive input , a negative input , a positive output , and a negative output electrically connected to it.
Finally, the NMOS gain-boost amplifier is electrically connected to and powered from a positive voltage power rail and a negative voltage power rail The following is also noted with respect to the gain-boost amplifiers , First, in a preferred embodiment, as shown in FIG.
Second, in a preferred embodiment, as shown in FIG. It will be apparent to those skilled in the art that many modifications and variations may be made to the above-disclosed embodiments of the present invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the disclosure and present invention and protected by the following claims.
Therefore, having thus described the invention, at least the following is claimed: 1. An operational amplifier comprising:.
Yes - you can combine two opamps with the aim to improve the overall peformance (not only for enlarging the open-loop gain). urken.xyz › document › apn › r13anboosting-op-amp-o. The op-amp operates as a non-inverting amplifier with the transistor as current booster. To prevent the feedback path from loading the circuit.