Multiplier Fundamentals — Lesson 1

This lesson covers the mixers or multipliers. It explains the role of mixers in a receiver, the importance of low noise amplifiers, and the concept of image reject filters. The lesson also delves into the general block diagram for a receiver and a transmitter, explaining the function of each block. It further discusses the concept of mixers as multipliers, the importance of differential amplifiers, and the impact of noise on the oscillator output. The lesson concludes with an introduction to the fully balanced double balanced mixer, also known as the Gilbert cell mixer.

Video Highlights

00:24 - Block diagram of receiver
07:40 - Explanation of the differential amplifier
22:49 - Explanation of the multiplication operation
30:13 - Importance of square waves in the local oscillator
42:18 - Potential problem with matching in the mixer

Key Takeaways

- Mixers or multipliers are crucial components in a receiver, typically serving as the second or third block.
- The first block in a receiver is usually a low noise amplifier, which is essential for reducing noise while maintaining gain.
- An image reject filter is often part of the low noise amplifier and plays a crucial role in a super heterodyne receiver.
- The mixer in a receiver has two inputs: a local oscillator and an RF signal. The frequency of these inputs determines whether the receiver operates in direct down conversion or heterodyne mode.
- The Gilbert cell RF mixer is a fundamental building block for all mixers on ICs.