Design of 2.4 GHz LNA, with programable gain

1. Variable Gain CMOS
LNA
Paulo Márcio, Fernando R. de Sousa

2. Abstract
•
It is presented here a variable gain low noise amplifier
(LNA) with differential output using a 0.18 μm CMOS
technology. The design of this LNA was specified for a
sigma-delta digital receiver, in accordance to the
IEEE802.15.4 standard using the industrial, scientific
and medical (ISM) band.

3. Problem to Solve
Paulo Marcio
(paulo.moreira@floripadh.com) 3

4. LNA's cores
Common Source Common Gate
50 Ω matching 50 Ω plus an imaginary part
Stability issues Stable
Inductors for the matching Don't use inductors for matching
NF depends on the FT Higher NF
Paulo Marcio
(paulo.moreira@floripadh.com) 4

5. Small signal model
Paulo Marcio
(paulo.moreira@floripadh.com) 5

6. LNA's load
2.2 k Ω
Paulo Marcio
(paulo.moreira@floripadh.com) 6

7. A gm Boost Configuration
At low frequencies
Paulo Marcio
(paulo.moreira@floripadh.com) 7

8. Cross coupled configuration
Paulo Marcio
(paulo.moreira@floripadh.com) 8

9. Low gain mode
Π Circuit
CG Circuit
Paulo Marcio
(paulo.moreira@floripadh.com) 9

10. Final Schematic
Paulo Marcio
(paulo.moreira@floripadh.com) 10

11. Simulations Results (Gain)
Paulo Marcio
(paulo.moreira@floripadh.com) 11

12. Simulations Results (NF)
Paulo Marcio
(paulo.moreira@floripadh.com) 12

13. Simulations Results (RL)
Paulo Marcio
(paulo.moreira@floripadh.com) 13

14. Comparison Table
*Voltage gain
[1] H. Alavi-Rad, Circuits and Systems for Communications (ECCSC), 2010 5th
European Conference on, pages 78–81, Mar. 2010.
[2] S. C. Blaakmeer, IEEE Journal of Solid-State Circuits, June 2008.
[3] X. Fan, H. Zhang, IEEE Journal of Solid-State Circuits, Mar. 2008.
[4] B. Park , Microwave Conference Proceedings (APMC), 2010 Asia-Pacific.

15. Test Structures
Paulo Marcio
(paulo.moreira@floripadh.com) 15

16. Layout
Paulo Marcio
(paulo.moreira@floripadh.com) 16

17. Conclusions

A LNA with variable gain is presented.

According to the simulation results It is possible to meet the
required specifications for the LNA.

Since the core consumption is reduced, an elegant way of
making the low gain mode is achieved.

This LNA is being fabricated using a 0.18 μm CMOS
technology.
Paulo Marcio
(paulo.moreira@floripadh.com) 17