Trouble using TG_TABLE_NAME in BEFORE INSERT OR UPDATE trigger

Using PostgreSQL 8.4.0, I have the following generic trigger defined for use
by a collection of the same structured tables:

CREATE OR REPLACE FUNCTION pdf_active_check() RETURNS trigger AS $BODY$
DECLARE
var_active BOOLEAN;
BEGIN
SELECT p.active INTO STRICT var_active FROM TG_TABLE_NAME pv INNER
JOIN pdfs p ON p.id = pv.pdf_id;
IF active THEN
RETURN NEW;
ELSE
RETURN NULL;
END IF;
END;
$BODY$ LANGUAGE 'plpgsql';

ERROR: syntax error at or near "$1"
LINE 1: SELECT p.active FROM $1 pv INNER JOIN pdfs p ON p.id = pv....
^
QUERY: SELECT p.active FROM $1 pv INNER JOIN pdfs p ON p.id = pv.pdf_id
CONTEXT: SQL statement in PL/PgSQL function "pdf_active_check" near line 4

When I try this kind of substitution with TEXT type variables, there isn't
any problem. I can imagine it has something to do with TG_TABLE_NAME being
of type NAME, but I can't find anything in the manual about the difference
or how to convert. Google wasn't much help either, but I figured this is
fairly trivial for those on this list...

Stephen Cuppett
steve at cuppett dot com