GaAs MMIC Low Noise Amplifier SOIC-8 Platform

Rev. V3

Application Note

M540

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Visit www.macomtech.com for additional data sheets and product information.

M/A-COM Technology Solutions Inc. and its affiliates reserve the right to make

changes to the product(s) or information contained herein without notice.

The AM50-0002 employs a combination of the LG and

HG designs to create a three stage, higher gain, LNA.

The AM50-0002, however, uses a simple external input

matching network to obtain minimum noise figure. A

detailed discussion of this external matching network is

contained in the section on customer use considerations.

In this product platform there are essentially two circuit

design types, a low gain (LG) and a high gain (HG). The

LG design (MAAM12022, MAAM12032, MAAM22010,

and AM50-0001), shown in Figure 3, employs a single

stage cascade configuration with series feedback to si-

multaneously achieve impedance match and minimum

noise figure.

The HG design (MAAM12021 and

MAAM12031), shown in Figure 4, uses two cascaded

common source stages biased in series to achieve the

high gain at low current consumption, and also employs

series feedback to simultaneously achieve impedance

match and minimum noise figure. The AM50-0002 em-

ploys a combination of the LG and HG designs to create

a three stage, higher gain, LNA. The AM50-0002, how-

ever, uses a simple external input matching network to

obtain minimum noise figure. A detailed discussion of

this external matching network is contained in the section

on customer use considerations.

The MMIC layout of Figure 5 is the MAAM12021, the

largest chip of the family; it measures 1 mm on a side.

Figure 6 illustrates the assembly of this MMIC into the

SOIC-8 package. Immediately one notices that the lead

frame is split and there is more than one chip in the plas-

tic package. The amplifier employs a custom fused split

paddle lead frame to ensure unconditional stability when

used on a typical FR4 board application. The other chip

in the package is a metal-nitride-silicon (MNS) single-

layer capacitor used for internal RF by-passing to allow

biasing from a single positive 3-5 V supply. These MNS

capacitors, supplied by M/A-COM’s Semiconductor Busi-

ness Unit, have almost ideal performance for very little

cost. After assembly, the MAAM12021 has the func-

tional diagram as shown in Figure 7. Six of the seven

LNAs in this product platform share these assembly and

functional diagrams. The AM50-0002 utilizes a slightly

different lead frame and pin assignment to accommodate

the special requirements of its three stage, high gain

design.

MMIC Manufacturing Considerations

The MMIC LNAs are automatically assembled onto cus-

tom designed, fused, split paddle lead frames as shown

previously in Figure 6. Careful consideration is given to

die placement, both for the GaAs MMIC LNA and the

MNS capacitor, to ensure repeatable bond wire induc-

tance and good mechanical strength for reliability. The

ground leads are fused to ensure low inductance

grounds as well as low thermal impedance. These fused

ground leads also lower cost in volume production by

eliminating eight ground bonds (2 per lead). Once as-

sembled onto the lead frames, the assembly is transfer

molded with a plastic which has both good moisture re-

sistance properties for reliability and well controlled di-

electric constant for repeatable RF performance. Fully

assembled MMIC LNAs are stored in antistatic tubes,

ready for automatic test.

Fully assembled MMIC LNAs are 100% RF tested for

compliance against the guaranteed data sheet perform-

ance of gain, nose figure, and DC current. Standard

automatic digital IC testers have been modified to make

rapid RF measurements.

Accuracy is maintained by

establishing correlation coefficients between the high

speed automated production testers and the highly accu-

rate engineering measurement system.

Quality and Reliability

The MMIC LNA products are subjected to a one-time

product qualification, either before product releases or

when there is a major process change. In the case of

the MMIC LNAs, the one-time qualification, according to

Table 1, has established the MMIC LNA product family to

be capable of serving the high volume global commercial

electronics market with a 400-FIT reliability rate (300

devices at an activation energy of 0.7 eV, normal operat-

ing temperature of 85˚C, and 90% confidence level).

The MMIC LNAs are also ESD classified as low level

class 1—as low as 350 volts can induce damage. Table

2 shows the on-going quality monitoring of plastic pack-

aged devices in production to maintain the established

level of product quality.

This 400-FIT reliability level is established at a junction

temperature of 150˚C or less. This is the reason for the

maximum rating on the data sheet of 150˚C or less. The

junction temperature can be calculated from the product

of the thermal resistance and power dissipated. The

thermal resistance for the MMIC LNAs is 165˚C/W on all

LNA’s, except for the AM50-0001 where it is 125˚C/W.