Differential Amplifier Bandwidth Peaking for Flat Gain to 20 GHz
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Solution Overview
Problem
It is challenging to fabricate an ultra wide band amplifier on a die as an integrated circuit with constant gain across a frequency band spanning from direct current (dc) to over 20 GHz, as existing technologies face difficulties in achieving this level of frequency response and gain consistency.
Innovation Solution
The amplifier incorporates a bandwidth peaking network with coils and resistors connected between a power supply and a core amplifier, along with a common mode bias network for voltage bias control feedback, to extend frequency response and maintain constant gain across the ultra wide band, while also handling differential input and output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a wide band amplifier is fabricated as an integrated circuit, then the amplifier can be integrated into IC form, but achieving constant gain across the entire frequency response from dc to over 20 GHz becomes difficult
Solution Approach 1:
The amplifier is divided into a core amplifier stage and a separate bandwidth peaking network. The core amplifier provides the basic amplification function, while the bandwidth peaking network (comprising inductors L1-L4 and resistors R1-R4) is added as a distinct segment to extend the frequency response and maintain constant gain across the ultra-wide band from DC to over 20 GHz.
Solution Approach 2:
The bandwidth peaking network utilizes carefully selected inductor and resistor values to shape the frequency response. By adjusting the L/R time constants of the peaking network components, the amplifier achieves substantially constant gain across the entire frequency band while maintaining IC compatibility.
2Adaptability or versatility
If the frequency bandwidth is extended to ultra wide band (dc to over 20 GHz), then the amplifier covers a broader frequency range, but maintaining constant gain across this band becomes increasingly difficult
Solution Approach 1:
The bandwidth peaking network acts as an intermediary between the core amplifier and the load. This network mediates the frequency response by using its L/R time constants to compensate for the core amplifier's gain roll-off at high frequencies, thereby extending the ultra-wide bandwidth while maintaining constant gain.
Solution Approach 2:
The bandwidth peaking network introduces frequency-dependent impedance characteristics that dynamically adjust the amplifier's response across the frequency band. The inductive and resistive elements create a frequency-selective feedback mechanism that actively maintains constant gain from DC to over 20 GHz.
3Adaptability or versatility
If a bandwidth peaking network with coils and resistors is added to extend frequency response, then the frequency bandwidth increases by up to 35%, but the device complexity increases
Solution Approach 1:
The bandwidth peaking network is integrated with the core amplifier in a unified IC structure. The inductors and resistors are combined with the amplifier transistors and biasing circuits into a single monolithic device, reducing overall complexity compared to discrete implementations while achieving 35% frequency response extension.
Solution Approach 2:
The bandwidth peaking network serves multiple functions simultaneously: it extends the frequency response, maintains constant gain, provides impedance matching, and stabilizes the amplifier across the ultra-wide band. This multi-functionality reduces the need for additional separate components or circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively increases the frequency response by up to 35% and maintains a constant gain level from dc to over 20 GHz, supporting differential signal processing with controlled impedances and low supply voltage, suitable for integrated circuit implementation.
Implementation Method 1
a bandwidth peaking network having a first coil and a first resistor connected in series, and a second coil and a second resistor connected in series
Implementation Method 2
The bandwidth peaking network is configured to increase the frequency bandwidth of the amplifier
Data Source
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AI summary
A wide band amplifier (10) includes a core amplifier (18) having input terminals and output terminals for, respectively, receiving differential input signals and providing amplified differential output signals. A bandwidth peaking network (14) is coupled to the core amplifier and includes (a) a first coil and a first resistor connected in series and (b) a second coil and a second resistor connected in series. The first coil and resistor and the second coil and resistor, respectively, are coupled to the core amplifier for receiving the amplified differential output signals. The bandwidth peaking network (14) is configured to increase the frequency bandwidth of the amplifier.