24-09-2015, 06:40 PM
The cathode resistor is mainly there to provide a DC path for the current through the valve. In an ideal world it would have infinite resistance but then no current would flow at all.
The input signal is between grid and 0V (ground). Not between grid and cathode. As far as signals are concerned, in an ideal world, the anode is at the same potential as ground so you could say the input signal is between grid and anode. But that's not a very helpful way of describing the cathode follower.
What's more interesting is that both input and output signals are referenced to 0V. This is unlike the common cathode configuration we normally see. Here the input (grid) is referenced to 0V while the output (anode) is referenced to HT+. I've said that the anode is at the same signal potential as 0V but this is only true in an ideal world. In practice the decoupling capacitors between HT+ and 0V are not perfect and neither is the HT+ supply. This imperfection gives rise to all sorts of practical problems in amplifiers including hum and instability.
The input signal is between grid and 0V (ground). Not between grid and cathode. As far as signals are concerned, in an ideal world, the anode is at the same potential as ground so you could say the input signal is between grid and anode. But that's not a very helpful way of describing the cathode follower.
What's more interesting is that both input and output signals are referenced to 0V. This is unlike the common cathode configuration we normally see. Here the input (grid) is referenced to 0V while the output (anode) is referenced to HT+. I've said that the anode is at the same signal potential as 0V but this is only true in an ideal world. In practice the decoupling capacitors between HT+ and 0V are not perfect and neither is the HT+ supply. This imperfection gives rise to all sorts of practical problems in amplifiers including hum and instability.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
