The following picture shows a part of a Gilber-Cell. The yellow part is a low-pass. The green one the mixer core and the blue one determines the operating point of the transistors.
Actually, my problem is to understand the setup for the operating point. Lets assume a Vcc of 5V and a voltage drop across RL of 0.4V. Then we have a collector node voltage at T1 of 4.6V. Now, the operating point has to be determined via the blue network consisting of base voltage dividers: and here I don't get everything.
What I think: The first diode causes a voltage drop of lets say 0.7V. Then I have a voltage divider. What base node voltage do I have to set up? Obviously it must be smaller than the collector node voltage. So, it must be smaller than 4.6V. My Question: How much smaller do I need to set up the base node voltage? Is it just necessary that it is smaller than the collector node voltage or must it be -0.7, so the opposite of Ube?