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AN644

Maxim Integrated Products
Part Number AN644
Manufacturer Maxim Integrated Products
Description QuickChip Design Example 2 Low Power Silicon BJT LNA for 1.9GHz
Published Mar 26, 2005
Detailed Description ASICs Application Note 644: Mar 17, 2000 QuickChip Design Example 2 Low Power Silicon BJT LNA for 1.9GHz 1998 IEEE. Re...
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AN644
AN644

Overview
ASICs Application Note 644: Mar 17, 2000 QuickChip Design Example 2 Low Power Silicon BJT LNA for 1.
9GHz 1998 IEEE.
Reprinted, with permission, from 1998 IEEE Microwave and Guided Wave Letters, Vol.
3, No.
3, pp.
136-137 Abstract A two-stage 1.
9GHz monolithic low-noise amplifier (LNA) with a measured noise figure of 2.
3dB and an associated gain of 15dB was fabricated in a standard silicon bipolar transistor array.
It dissipates 5.
2mW from a 3V supply including the bias circuitry.
Input return loss and isolation are -9dB and -20dB, respectively.
I.
Introduction In portable communication equipment, such as cellular phones and digital cordless phones, manufacturers are trying to replace as many discrete devices as possible with high-density ICs to be competitive in size, weight, power dissipation, and price.
In a number of recent papers low power LNAs for S-band have been described [1,2,3].
These LNAs were fabricated using some sophisticated GaAs full-custom processes.
Since the high frequency performance of stateof-the-art silicon bipolar processes are continuously improving lowcost semi-custom arrays with a limited choice of components provide a reasonable solution for RF applications.
In order to demonstrate such a solution, we present in this letter a very low-power monolithic 1.
9GHz silicon LNA which draws a total current of 1.
75mA including bias circuit.
II.
Circuit Design A schematic of the two-stage LNA is shown in Fig.
1.
The circuit employs a high-gain common-emitter stage (Q1-RL) and a emitter-follower output stage (Q2-Q3).
This approach eliminates the need for coupling capacitors.
The current of the first stage is set by a resistive parallel feedback (R3 and R4), which is connected to the external matching inductor (L1) such that no noise degradation occurs.
Thus, only a single supply voltage is required.
This feedback also improves both the bias and RF stability of the amplifier.
www.
maxim-ic.
com/an644 Page 1 of 6 Figure 1.
Simplified schematic of th...


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