Today I opened up an old mobile phone made by Ericsson. It's called an A1018s, one of those brick-shaped things with an antenna that were common in the late 1990's. Mobile phones are interesting devices from an electronic point of view, because their designers have had to squeeze a huge amount of CPU power, a couple of very high-frequency radio receivers and transmitters, and a high-capacity battery all into something small enough to slide into your pocket. No wonder it's taken mankind six millennia to get there ;-)

This is the top of the main circuit board from this phone. The circuitry on here is divided into two parts, with the part at the top probably being the transmitter and the lower part being the receiver. There is a third part (not shown in this picture) with the main controller CPU, but that's all just digital stuff which, as we all know, is boring compared to high-frequency analogue electronics. In this article I'm going to show the inside of the two big ICs shown in this photo. It's quite hard to track down what these do exactly, there is very little information available on the internet about these devices.

The chip at the upper left is marked as:

SP931 38043

R081011100/C

R1A6001243.1

While the one on the lower right is called:

3004CR1C

Q3959

MPJ

99371

Anyway, for now I've called them 38043 and R8541, because that's the numbers shown on the ICs themselves, as you'll see on the following pages. In the picture above there are also a couple of metal boxes. These contain hybrid circuits, which are like halfway between a PCB and an IC (hence the name). They are very small PCBs with tiny SMD parts soldered on, together with a couple of bare semiconductors (transistors etc). This setup is used for things like RF amplifiers, because the circuits need to be both small and able to handle a lot of power, exactly the two properties inherent in this setup.

On to the ICs then!