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Current mirror in a bandgap reference

I was looking through some of the example circuits that come with LTSpice, and there's a file with some bandgap voltage references. I'm unfamiliar with the current mirror arrangement in the following schematic...the transistor directly above Out is an NPN, not the PNP I would expect for something like a Wilson current mirror. If I switch it to a PNP, the circuit doesn't work properly anymore. For the bandgap to work properly I'm assuming that Q1 must have a larger emitter area than Q2 to generate a Vbe differential. Any insight would be appreciated!

VCC -+ | ------------- | | >| |< Q5 |---o---| Q4 /| | |\ o | | | '-----o | | | |/ .-------o-| Q3 | |>

| .--- | | Out | .-. | | | | | | | '-' | .------' \| | | Q2 |--o- |/

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It's a cascode, allowing a current path that's not resistive. ...Jim Thompson

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