I do not understand section 8.6 of my lecture notes (see the attachment). 1. "If two low pass filters are cascaded the output voltage is not simply the product of two transfer functions." : Why not? Why would we even think of multiplying two transfer functions? Which transfer functions are being referred to? Why? 2. "If you try to analyse such a circuit using phasors and an Argand diagram you will soon realise the shortcomings of that technique. This is because the second filter acts as a load for the first." : Could someone please explain how the second statement leads to the first statement? 3. "However, we shall later that a simple operational amplifier circuit called the unity gain buffer acts as an impedance matcher so that loading of the first filter by the second does not occur. " : What is an impedance matcher? Why does the loading not occur due to an impedance matcher? Thanks in advance for any help.