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RT9161-50GX_Datasheet PDF

时间:2021-06-14 02:10:55 来源:网络整理编辑:eConais

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The new technology also promises enormous energy savings to broadcast stations. Until now, the power bill of the most powerful transmitter networks accounted for up to 80 percent of operating costs.

The new technology also promises enormous energy savings to broadcast stations. Until now, the power bill of the most powerful transmitter networks accounted for up to 80 percent of operating costs.

at 25C. Therefore, the noise current through Re develops a noise voltage that is:

RT9161-50GX_Datasheet PDF

Following through on the algebra:

RT9161-50GX_Datasheet PDF

Here it is seen that the voltage noise goes down as one over the square root of the collector current. In order to get lower noise the collector current must go way up.

As an example, assume a collector current of 1.25mA. The resulting noise voltage is 0.42nV/sq-rt Hz. Notice that all of the calculations here are noise density values and therefore have the root-Hz unit modifier.

RT9161-50GX_Datasheet PDF

This is half of the input stage of an operational amplifier. The other half of the differential pair would contribute the same magnitude noise but uncorrelated. As these are independent noise sources they collect as the root-sum-square. The total of the two devices would be 1.414 times the noise from one.

If we turn this relationship around the input stage current necessary to get to a noise density of 1nV/sq-rt Hz is 432uA per transistor, or 862uA for the input stage. A good estimate is that half of an op amp quiescent current is through the input transistors and half is used for the rest of the device. Therefore, under ideal conditions the total device quiescent current for a 1nV/sq-rt Hz op amp will be over 1.7mA.

Broadcom made a big splash by being first to market with an 802.11g chip set. The company is benefiting from rapidly growing interest in the 11g, which combines the blazing speed of 11a with the greater indoor range of 11b.

Using its strength in mixed-signal design, Broadcom has produced a single-chip radio with a direct-conversion design that eliminates the bulky external SAW filter. Broadcom's integrated MAC/BB chip offers both WEP/WPA and AES support for the future 802.11i standard.

Because Broadcom's radio is an all-CMOS design, the company has the inside track to deliver a single-chip 802.11 product. We anticipate such a design will enter production in mid-2004. If they execute well, Broadcom and Intel are likely to become the market leaders by 2005.

As for the startups, the 802.11 market looks like another case of herd investing. With total chip revenue of $500 million to $600 million in 2005 and most of that going to large companies, few startups will survive, and fewer still will provide a return on investment.

Linley Gwennap is founder and principal analyst of The Linley Groupa(www.linleygroup.com).